


...,.' 
























^ 



^ v y 












X 



A COMPLETE TREATISE 



ECTRO-DEPOSITION OF METALS. 



COMPRISING 

ELECTRO-PLATING AND GALVANOPLASTIC OPERATIONS, THE DEPOSITION OF METALS 

BY THE CONTACT AND IMMERSION PROCESSES, THE COLORING OF METALS, 

THE METHODS OF GRINDING AND POLISHING, 

AS WELL AS 

DESCRIPTIONS OF THE ELECTRIC ELEMENTS, DYNAMO-ELECTRIC 

MACHINES, THERMO-PILES, AND OF THE MATERIALS AND 

PROCESSES USED IN EVERY DEPARTMENT OF THE ART. 

TRANSLATED FROM THE GERMAN OF 

DR. GEORGE LANGBEIN, 

PROPRIETOR OF A MANUFACTORY FOR CHEMICAL PRODUCTS, MACHINES, APPARATUS, 

AND UTENSILS FOR ELECTROPLATERS AND OF AN ELECTRO-PLATING 

ESTABLISHMENT, IN LEIPZIG. 



/' 






WITH ADDITIONS BY 

WILLIAM T. BRANNT, 

EDITOR OF "THE TECHNO-CHEMICAL RECEIPT BOOK." 



FOURTH EDITION, THOROUGHLY REVISED AND MUCH ENLARGED. 

ILLUSTRATED BY ONE HUNDRED AND S'XTv ENGRAVINGS. 



PHILADELPHIA: 
HENRY CAREY BAIRD & CO., 

INDUSTRIAL PUBLISHERS, BOOKSELLERS, AND IMPORTEKS. 

810 WALNUT STREET. 

1902. 



1 *(\V 



THE UBRARY «F 

QOHQRESS, 
Two Comee Receive* 

FEB. 10 1902 

C«3PV«|QHT ENTRY 

CLASS ^ XXc N©. 

Z- £> *} <W 

copy a 



Copyright by 

HENEY CAREY BAIRD & CO., 

1902. 



(7 s 



Printed at the 
WICKERSHAM PRINTING HOUSE 

53 and 55 North Queen Street, 
Lancaster, Pa., U. S. A. 



PREFACE TO THE FOURTH AMERICAN EDITION. 



THE rapid sale of the third American edition of Dr. George 
Langbein's work, Vollstandiges Handbuch der Galvanischcn 
Metall-Niederschlage, and the continued demand for it, may be 
accepted as the best proofs of the value and usefulness of the 
book. 

In the arrangement of the text in this, the fourth edition, now 
presented to the public, but few changes have been made. A 
number of new processes and improvements in older methods 
which have become known, and have been practically tested, 
since the publication of the previous editions, have been in- 
cluded, as well as the most recent machinery and apparatus, 
and special sections have been devoted to the quantitative 
determination of the contents of the baths most generally 
employed. 

The editor is under obligations to the Hanson & Van Winkle 
Co., of Newark, N. J., the well-known manufacturers of, and 
dealers in, electro-platers' supplies, for valuable information and 
engravings. 

The publishers have spared no expense in the proper illus- 
tration and the mechanical production of the work, and, like 
the previous editions, it has been provided with a copious table 
of contents and a very full index, so as to render reference to 
any subject prompt and easy. 

W. T. B. 

Philadelphia, February i, 1902. 

(iii) 



PREFACE TO THE FIRST AMERICAN EDITION. 



The art of the electro-deposition of metals has during recent 
years attained such a high degree of development that it was 
felt that a comprehensive and complete treatise was needed to 
represent the present advanced state of this important industry. 
In furtherance of this object, a translation of Dr. George Lang- 
bein's work, Vollstandiges Handbuch der Galvanischen Metall- 
Niederschlage, is presented to the English-reading public with 
the full confidence that it will not only fill a useful place in 
technical literature, but will also prove a ready book of reference 
and a practical guide for the workshop. In fact, it is especially 
intended for the practical workman, wherein he can find advice 
and information regarding the treatment of the objects while in 
the bath, as well as before and after electro-plating. The au- 
thor, Dr. George Langbein, is himself a master of the art, being 
the proprietor of an extensive electro-plating establishment 
combined with a manufactory of chemical products, machinery 
and apparatus used in the industry. 

The results yielded by the modern dynamo-electric machines, 
to which the great advance in the electro-plating art is largely 
due, are in every respect satisfactory, and the more so since the 
need of accurate, and at the same time handy, measuring in- 
struments has also been supplied. With the assistance of such 
measuring instruments, the establishment of fixed rules regard- 
ing the current-conditions for a galvanic bath has become pos- 
sible, so that good results are guaranteed from the start. While 
formerly the electro-plater had to determine the proper current- 
strength for the depositions in an empirical manner, by time- 
consuming experiments, to-day, by duly observing the deter- 

(v) 



vi PREFACE TO THE FIRST AMERICAN EDITION. 

mined conditions and provided with well-working measuring 
instruments, he can at once produce beautiful and suitable 
deposits of the various metals. 

The data referring to these current-conditions, according to 
measurements by Dr. Langbein, are given as completely as pos- 
sible, while for the various baths, only formulae yielding entirely 
reliable results have been selected. To most of the baths a 
brief review of their mode of action and of their advantages for 
certain uses is added, thus enabling the operator to select the 
bath most suitable for his special purpose. To the few formulae 
which have not been tested, a note to that effect is in each case 
appended, and they are only given with due reserve. 

To render the work as useful as possible, the most suitable 
formulae for plating by contact and immersion, as well as the 
best methods for coloring the metals, and the characteristic 
properties of the chemicals used in the industry, are given. 
However, the preparation of the chemicals has been omitted, 
since they can be procured at much less expense from chemi- 
cal works than it would be possible for the electro-plater to 
make them in smali quantities, even if he possessed the neces- 
sary apparatus and the required knowledge of chemistry and 
skill in experimenting. 

It is hoped that the additions made here and there by the 
translator, as well as the chapter on " Apparatus and Instru- 
ments," and that of " Useful Tables," added by him, may con- 
tribute to the usefulness of the treatise. 

Finally, it remains only to be stated that the publishers have 
spared no expense in the proper illustration and the mechani- 
cal production of the book ; and, as is their universal practice, 
have caused it to be provided with a copious table of contents, 
and a very full index, which will add additional value by 
rendering any subject in it easy and prompt of reference. 

W. T. B. 

Phlladelphia, July i, 1891. 



CONTENTS. 
I. 

HISTORICAL PART. 



CHAPTER I. 
Historical Review of Electro-Metallurgy. 

PAGE 

The method of coating metals by simple immersion known to Zozimus 
and Paracelsus; Luigi Galvani's discovery, in 17^9, of the electric 
contact-current; Alexander Volta's discovery, in 1799, of the true 
causes of the electric-contact current; Galvani's experiments . . 1 

Erroneous inference drawn by Galvani from his experiments; General 
ignorance in regard to the electric current; Discovery which led to 
the construction of the pile of Volta, or the voltaic pile; Cruik- 
shank's trough battery 2 

Decomposition of water by electrolysis by Nicholson and Carlisle, 1800; 
Wollaston's observations, 1801; Cruikshank's investigations, 1803; 
Brugnatelli's experiments in electro-gilding, 1805; Sir Humphrey 
Davy's discovery of the metals potassium and sodium, 1807; Prof. 
Oersted's discovery of the deflection of the magnetic needle, 1820 . 3 

Construction of the galvanoscope or galvanometer; Ohm's discovery, 
in 1827, of the law named after him ; Faraday's discovery in 
1831, of electric induction; First electro-magnetic induction machine 
constructed by Pixii; Faraday's electrolytic law laid down and proved 
in 1833; Production of iridescent colors, in 1826, by Nobili; Produc- 
tion of the amalgams of potassium and sodium, in 1853, by Bird . 4 

Discovery of the actual galvanoplastic process, in 1838, by Prof. Jacoby; 
Claims of priority of invention by Mr. T. Spencer, and by C. J. 
Jordan; Labors of the Elkingtons, and of De Ruolz; Murray's dis- 
covery, in 1840, of black-leading; Introduction, in 1843, of gutta- 
percha by Dr. Montgomery; First employment, in 1840, of alkaline 
cyanides by Wright 5 

Patent for the deposition of nickel, 1840; Origination of the term 
"electrometallurgy" by Mr. Alfred Smee, 1841; Prof. Boettger's 

(vii) 



Vlll CONTENTS. 

PAGE 

discovery, in 1842, of the deposition of nickel from its double salt; 
First deposition of metallic alloys by De Ruolz; First use of thermo- 
electricity, in 1843, by Moses Poole; Advances in the art of electro- 
deposition 6 

The first magnetic machine that deposited silver on a practical scale 
constructed, in 1844, by Woolrych; Attempts, since 1854, by Christ- 
ofle & Co. to replace their batteries by magneto-electrical machines; 
The Alliance machine 7 

Objections to Wilde's machine; Dr. Antonio Pacinotti's invention, in 
i860, of the ring named after him; Siemens' dynamo machine, 1866; 
Wheatstone's dynamo machine, 1867; Introduction, in 187:, ofZenobe 
Gramme's machine; Siemens & Halske's machine, 1884; S. Schuck- 
ert's machine, 1884 8 

Various European and American constructions of dynamo-electrical 
machines; Investigators and practitioners who have contributed to 
the improvement of the electro-chemical processes and the perfection 
of galvano-plasty . . 9 



IT. 

THEORETICAL PART. 



CHAPTER II. 
Magnetism and Electricity. 

i. magnetism. 

Loadstone or magnetic iron ore; Natural and artificial magnets; Defini- 
tions of the magnetic poles and of the neutral line or neutral zone . 10 

Magnetic meridian; North and south poles; Phenomena of attraction 
and repulsion; Ampere's theory 11 

The solenoid; Rejection of Ampere's theory by many scientific men; 
Definition of the magnetic field 12 

2. ELECTRICITY. 

Definition of idio-electrics and non-electrics; Gray's discovery; Good 
and bad conductors; The electroscope; Existence of two kinds of 
electricity, Vitreous, or positive, and resinous, or negative electricity. 13 

Double fluid hypothesis of electricity; Single fluid hypothesis of elec- 
tricity 14 



CONTENTS. IX 

PAGE 

Investigations of Prof. Herz; Coulomb's law; Series of electro-motive 
force or tension ........... 15 

The galvanic current or hydro-electric current; Galvanic element or 

galvanic chain; Electrical potential; Electro-motive force; Resistance. 1(3 
Conducting power of metals; Quantity of current — Ohm's law . . 17 
Essential or internal resistance; Non-essential or external resistance . 18 

Coupling of elements in various ways 19 

Coupling of elements for electro-motive force or tension; Coupling for 
quantity of current; Mixed coupling; Proposition deduced from Ohm's 

law 20 

Effects of the eletric current 21 

Electro- magnetism . 

Rule for determining the direction which the magnetic needle will as- 
sume when placed in any particular position to the conducting wire. 21 

Galvanoscope, galvanometers or multipliers ; The astatic galvanometer; 
The tangent galvanometer; The sine galvanometer . . . .22 

Electro-magnets; The solenoid; Law of the action of two electrified 
wires on each other 23 

Induction . 

Definition of induction .......... 23 

Primary or inductive current; Secondary, induced or induction-current. 24 
Alternating currents; Extra currents . 25 

Chemical Action of the Electrical Current — Electrolysis. 

Reduction of the constituents of a fluid by the electric current; Pure 

water a bad conductor . . .25 

Faraday's discovery of the chemical actions of the electric current; 
Electrolysis; Electrolyte; Electrodes; Anode; Cathode; Ions; Anions; 
Rations; Atoms; Clausius' theory of the composition of matter . 26 

Counter or polarizing current; Svante Arrhenius' theory of electrolytic 
dissociation; Electrolytes; Classification of the ions . . . .27 

Table of most important ions; Formation of ions 28 

Hittorfs's experiments; Osmotic pressure 29 

Explanation of the formation of the polarizing current; Faraday's elec- 
trolytic laws 30 

Local action; Electro-chemical equivalents; Joule's law . . .32 

Consumption of power in electrolysis; Electric units adopted by the 
International Congress of 1881; Fundamental or C. G. S. (centimetre- 
gramme-second) units; Force or power — dyne; Work — erg; Quantity; 

Potential or electro-motive force 33 

Resistance; The ohm; The ampere; The volt; The farad; The coulomb; 
The watt; Definition of English and of French horse-power . . 34 



CONTENTS. 
III. 

SOURCES OF CURRENT. 



CHAPTER III. 

Galvanic Elements— Thermopiles — Magneto- and Dynamo- 
Electric Machines. 

a. galvanic elements. 

PAGE 

The voltaic pile; Trough battery 35 

Reduction of local action by amalgamating the zinc; Various ways of 

amalgamation . . 36 

Bouant's recommendation; Definition and cause of polarization; Smee's 

element , 37 

Constant elements; Daniell's element ....... 38 

Meidinger element 39 

Grove element; Bunsen elements 40 

Improved Bunsen cell 42 

Electropoion and its composition; Best location of elements . . .43 
Dupre's substitute for sulphuric and nitric acids for filling elements; A 

soluble chromium combination which depolarizes with rapidity . . 44 
Inspection and cleansing of the binding screws; Manipulation of Bun- 
sen elements . . . . . . . . . . . .45 

Advisability of having a duplicate set of porous clay cells; Renewal of 

the acid; Foote's pinnacle gravity battery 46 

Oppermann's element . . . . . . . . .47 

Leclanche element; Lallande and Chaperon element . . . .51 

The cupron element 53 

Various elements; Dun's potash element 54 

Element patented by Knaffe and Kiefer, of Vienna . . . .55 

Plunge or bichromate batteries; The Bunsen plunge battery; Fein's 

bichromate battery . . , 56 

Keiser and Schmidt's bichromate battery ...... 57 

Bichromate element for gilding or silvering small articles . . .58 
Stoehrer's element; Plunge element manufactured by Dr. G. Langbein 

& Co 59 

B. THERMO-E1ECTRIC PILES. 
Prof. Seebeck's discovery, in 1822, of a new source of electricity . . 60 



CONTENTS. XI 

PAGE 

Definition of a thermoelectric couple and of thermo-electricity; Noe's 
thermo electric pile; Clamond's thermo-electric pile . . . .61 

Hauck's thermo-electric pile 62 

Giilcher's thermo electric pile . . . . . . . .63 

C MAGNETO- AND DYNAMO-ELECTRIC MACHINES. 

Faraday's discover}', in 1831 65 

Magnetic field or the region of the lines of force; What a magneto- 
electric or dynamo-electric machine actually is 66 

Prof. S. P. Thompson's definition of a dynamo-electric machine . . 67 
Pixii's electrical machine, 1832; Saxton and Clarke's improvements; 
Dr. W. Siemens' improvement, 1857; Pacinotti's ring armature, i860; 
Dr. W. Siemens' and Sir C. Wheatstone's simultaneous discovery . 68 
Classes of electric generators; Continuous current and alternating cur- 
rent machines; The Gramme machine 69 

The Gramme armature; Modern Gramme dynamo for galvanoplastic 

purposes 70 

Disadvantage of the Gramme machine -71 

S. Schuckert's flat ring machine 72 

Substitution of a dynamo of the drum-armature type for the flat ring 

machine; Fein's dynamo machine 73 

Siemens & Halske's dynamo-electric machines 74 

Kroettlinger dynamo .......... 76 

Lahmeyer dynamo . . . . . . . . . . .77 

Shunt-wound dynamo constructed by Dr. G. Langbein &Co.; Armature 

of this dynamo 79 

Resume of the evolution of the dynamo for plating purposes in the 

United States 80 

The Weston dynamo; "Little Wonder" dynamo; The "Wonder" 

dynamo 81 

The new Hanson & Van Winkle dynamo 82 

Direct connected motors to machines; Mode of connecting the generator 

and motor 85 

Various dynamo machines; Value of the dynamo, and its effect upon 

the electro-plating industry 86 

Data for the most suitable machine 87 

D. SECONDARY ELEMENTS (ACCUMULATORS). 

Planters practical application of accumulators, and his accumulator . 87 

Faure's use of lead grids . . - 88 

Storage capacity of accumulators; Chemical processes which take place 

in the accumulator; J^lbs's theory 89 

Liebenow and Loeb's theory .90 

Common form of an accumulator; Charging the accumulator; Diagram 
showing the connection of a plant as installed by the Electro- Chemical 
Storage Co. of New York 91 



Xll CONTENTS. 

IV. 

PRACTICAL PART. 



CHAPTER IV. 
Arrangement of Electro-Plating Establishments in General. 

PAGE 

Necessity of sufficient light and thorough ventilation . . . .93 
Location of Bunsen elements; Provision for heating . . . .94 
Importance of a good supply of water; Best materials for floors . . 95 
Size of the operating room ; Grinding and polishing rooms . . .96 
Prevention of dust in the polishing room; Location of the transmission 
carrying the belt pulleys ......... 97 

ELECTRO-PLATING ARRANGEMENTS IN PARTICULAR. 

Parts constituting the actual electro-plating plant; Arrangement with 

elements 97 

Choice of coupling the elements; Proportion of the effective zinc surface 

of the elements to that of the anodes and articles .... 98 

Requisites as regards the result of the process of deposition . . .99 
Coupling of elements for thick, solid, and thin deposits . . . . 100 
Auxiliary apparatus; The rheostat, current-regulator, resistance-board 

or switch board 101 

Conditions upon which the action of the resistance-board is based . 102 

Horizontal and vertical galvanometers 103 

Location of the resistance-board and galvanometer; Improved H. and 
V. W. patent underwriter's switch-board ...... 104 

Indications made by the galvanometer ....... 106 

Positive or anode wire; Negative or object wire; Vats or tanks; Wooden 

vats and their construction 109 

Wooden vats lined with sheet lead for acid copper and nickel baths . 110 
Objections to such vats; Enameled iron vats; Agate vessel for gold and 

other solutions Ill 

Conducting rods; Anodes and their arrangement 112 

Binding posts and screws; Mode of suspending the anodes . . . 113 
Mode of suspending the objects; Slinging wires; Protection of the con- 
ducting rods; Cleansing and rinsing apparatus 114 

Dipping or pickling; Sawdust for drying the objects; Arrangement with 
dynamo-electric machines; Rules for setting up and running a 

dynamo . 115 

Insulation of the object- and anode- wires; Special wire carriers; Ar- 
rangement with one machine which has to feed several baths . .117 



CONTENTS. Xlll 

PAGE 

Scheme of a dynamo, with the auxiliary apparatus, the main conduct- 
ing wire and a few baths; Location of the dynamo rheostat: The am- 
peremeter or ammeter, and the voltmeter; On what the character of 
a deposit obtained in a certain solution largely depends . . .118 

The Starrett improved voltmeter 120 

The little H. & V. W. voltmeter; The Weston voltmeter . . .121 

The Weston ammeter 122 

Scheme showing the coupling of the main object wire and the main 
anode wire with the resistance-boards, the voltmeter, the switch, and 

two baths 123 

Ground-plan of an electro-plating establishment 125 

Table for freeing the articles from grease 127 

Plating-room arranged by the Hansen & Van Winkle Co., of Newark, 
N. J. ; Mode of calculating the thickness of the conducting wires for 
dynamos 129* 

CHAPTER V. 

Treatment of Metaeuc Articles. 

a. mechanicae treatment. 

Treatment before electro-plating; Scratch-brushing; Formation of the 

deposit in correspondence with the surface of the basis-metal . . 132 
Modes of scratch-brushing; Various forms of brushes .... 133 
Treatment of scratch-brushes; Circular scratch-brushes .... 134 
Circular scratch-brush for cleaning purposes, and its construction . 135 

Brushes; Use of sand blast for cleaning . 13(> 

The La Pierre patent sand blast; Other types of sand blasts . . . 137 

Sand blast combined with a scouring drum 138 

Cleaning metallic surfaces in the tumbling barrel or drum . . . 139 

Adjustable oblique tumbling barrel 141 

Grinding; Grinding wheels and their construction 142 

Grinding wheels of pasteboard and of cork waste . ." . . 143 

Roughing wheel, medium wheel, and fine wheel; Treatment of the 

grinding wheels 144 

Vienna lime; Grinding lathes 145 

Execution of grinding; Fibres 146 

Fibre brushes; Grinding iron and steel articles 147 

Grinding brass and copper castings, sheets of brass, German silver and 

copper, zinc castings, sheet zinc; Polishing 148 

Foot-lathe for polishing; Cloth bobs; Union canvas wheel; Walrine 

wheel 149 

Foot-power grinding and polishing lathe ; Double polishing lathes; 

Lathe manufactured by the Hanson & Van Winkle Co. . . . 150 
Electrically driven grinding and polishing lathes 152 



xiv CONTENTS. 

{page 
Glue pot; Belt strapping attachment or endless belt machine . . 153 

Flexible shafts for grinding, polishing and buffing 154 

Polishing materials; Rouge composition 155 

Burnishing; Mechanical treatmeut during and after the electro plating 
process; Scratch-brushing the deposits . ...... 156 

Effect of scratch-brushing; Scralch-brushes used for different metals; 

Decoctions used in scratch-brushing 157 

Scratch-brushing by hand . 158 

Lathe-brush; Treatment of the finished electro-plated objects; Sawdust 
for drying the objects; Method of freeing nickeled objects from 

moisture . 159 

Polishing deposits of nickel, copper, brass, tin, gold and silver and pla- 
tinum; Operation of burnishing and forms of burnishers . . .160 

B. CHEMICAI, TREATMENT. 

Pickling and dipping; Mixture for pickling cast-iron and wrought-iron 
objects; Excellent pickle for iron; Pickling in the electrolytic way; 
Duration of pickling .......... 162 

Pickling zinc objects; Cleansing and brightening copper and its alloys, 
brass, bronze, tombac and German silver; Preliminary pickle; Bright- 
dipping bath 163 

Use of potassium cyanide for pickling; Handling of pickled objects; 

Matting 164 

Matting by chemical means; Mixture for the production of a matt- 
grained surface by pickling; Matting by mechanical means . ., 165 
Matting by galvanoplasty; Main points in pickling . . . .166 

Absorbing plant for escaping acid vapors ...... 167 

Regaining of acid and metal from exhausted dipping baths . . . 168 
Removal of grease and cleansing ........ 169 

Preparation of lime mixture; Cleansing with benzine .... 170 

Tying the objects to metallic wires; Removal of oxide from the metallic 

objects 171 

Steel spring carboy rocker 172 

CHAPTER VI. 
Processes of Electro-Deposition. 

Importance of the constitution of the water used as a solvent; Spring 
and well water; Rain water 173 

Importance of the purity of the chemicals used; Examples of difference 
in chemicals 174 

Concentration of the baths; Non-reliability of measurement by hydro- 
meter degrees 175 

Effects of baths too poor in metal, and too concentrated; Stirring up the 
baths 176 



CONTENTS. XV 



Effect of heavier and more saturated fluid on the anodes; Constant agi- 
tation of the baths by mechanical means; Advantage of constant agi- 
tation in silvering and in galvano-plastic operations . . . .177 

Bossard mechano-electroplating tanks . . . . . . .178 

Electro-plating apparatus for mechanical electro-plating, patented by 
the Electrolytic Plating Apparatus Co., of Walsall and Birmingham, 
England; Temperature of the baths 180 

Boiling of the baths; Kettles and boiling pans; Solution of nickel salts 
dissolving with difficulty 181 

Eiltration of the boiled solutions; Means of securing lasting qualities to 
the bath; Choice of anodes 182 

Alloying of the deposit with the basis-metal; Gore's experiments . . 183 

Conditions for the good performance of an electrolytic bath; Reduction 
of metals without a battery (electro-deposition by contact) . .184 

Reduction of metal by dipping one metal into one fluid . . . . 185 

CHAPTER VII. 

Deposition of Nicked and Cobalt. 

i. nickeling. 

■Growth and popularity of nickel-plating; Properties of nickel . . 186 
Nickel baths; General rules for preparing nickel baths; The active con- 
stituent in many prepared nickeling salts .... . 187 
Use of the chlorine combinations; Additions to the nickel bath recom- 
mended by various experts; Effects of the presence of small quauti- 
tities of free acid; Boric acid as an addition to nickeling and all other 

baths . . .188 

Action of boric acid; Determination of the acidity, alkalinity and neu- 
trality of nickel baths 189 

Formulae, preparation, characteristics and treatment of nickel baths . 190 
Burning or over nickeling . . . . . . . . . 191 

Nickel baths containing boric acid; Weston's bath ..... 192 

Xaselowsky's formula; Preparation of a nickel bath containing boric 

acid 193 

Nickel baths for special purposes . . . . . . . .194 

Bath for nickeling of a dark tone ........ 195 

Compositions of a few nickel baths which have been highly recom- 
mended; An English formula; Addition of bisulphide of carbon to 
nickel baths; Bath for nickeling small articles; Bath for the produc- 
tion of very thick deposits 196 

Correct working of freshly-prepared nickel baths; Cause of the deposi- 
tion of somewhat more brittle nickel by freshly -pre pared baths; Peel- 
ing off of the deposit 197 

Nickel bath without nickel salt; Nickel anodes 198 



XVI CONTENTS. 

PAGE 

Objections to insoluble anodes 199 

Use of rolled and cast anodes together in one bath 200- 

Size of an ode- surface; Cause of a reddish tinge on the anodes; Manner 
of suspending the anodes; Restoration of the neutrality, or of a slightly 
acid reaction of a nickel bath; Process of nickeling .... £02. 
Coppering or brassing articles previous to nickeling .... 203 

Suspension of the objects in the bath 204 

Suitable current-strength for nickeling; Burning or over-nickeling . 205. 
Criteria for judging whether the nickeling progresses with a correct 
current-strength; Density of current most suitable for nickeling . £06 

Solid nickeling - . . 207 

Test for sufficiently heavy nickeling; Arrangement of object-rods and 

anode-rods; Most suitable distance of the anodes from the object . 208 
Use of the hand-anode; Additional rules for nickeling and other electro- 
plating processes; Rules for suspending the objects in the bath . . 209 

Polarizing phenomena 210* 

Nickeling en masse of small and cheap objects 211 

Warren's solutions of nickel and of cobalt to be decomposed in a simple 
cell apparatus ; Contrivances for electro -plating small articles en 

masse 213 

Dr. Geo. Langbein & Co.'s apparatus for this purpose; Plating drum 
recommended by Pfanhauser ......... 214 

Rocking apparatus patented by Dr. Geo. Langbein & Co. for plating 
rods, bicycle spokes, chains, etc.; Arrangement for suspending 

bicycle spokes in the bath . . . - 216- 

Stripping nickeled articles; Stripping acid . . . . . .217 

Stripping by brushing; Stripping by means of the battery or the 
dynamo; Remedy against a yellowish tone of nickeling; Resume 
of the principal phenomena which may occur in nickeling, and their 

avoidance 218 

Refreshing nickel baths 220 

Treatment of articles after nickeling; Polishing nickel deposits; Treat- 
ment of articles which are to remain matt; Nickeling sheet zinc . 221 
Preliminary grinding and polishing; Construction of cloth bobs . . 222 

Mode of polishing or grinding the sheets 223 

Self-acting sheet polishing machines; F. Rauber's sheet-grinding and 

polishing machine 224 

Automatic sheet-polishing machine constructed by F. W. Koffler, of 

Vienna 228 

Automatic sheet-polishing machine constructed by Friedr. Krupp, 
Grusonwerk, Magdeburg- Buckau, Germany ..... 230 

Cleansing zinc sheets; Nickeling the sheets ...... 232 

Advantages of previous coppering or brassing; Prevention of the peel- 

ing-off of the nickel deposit 233 

Coppering the sheets; Dimensions of vats for nickeling the sheets . 234 



CONTENTS. xvil 

PAGE 

Anodes used for nickeling sheet-zinc, and proportion of anode-surface 

to zinc-surface; Cause of black streaks and stains .... 235 

Augmentation of the metallic content of the bath; Polishing the nickeled 

sheets; Nickeling tin-plate, Nickeling copper and brass sheets . . 236 
Nickeling sheet-iron and sheet-steel ....... 237 

Nickeling wire and apparatus for that purpose 238 

Nickeling wire-gauze; Nickeling knife-blades, sharp surgical instru- 
ments, etc 240 

Nickeling skates ........... 241 

Nickeling printing plates (electrotypes, cliches, etc.); Hard nickeling 

and baths for that purpose 242 

Recovery of nickel from old baths; Urquhart's plan for recovering nickel 

from old solutions; To improve defective nickeling .... 244 
Arrangement of the "doctor;" Nickeling by contact and boiling . 245 
Deposition of an alloy containing nickel according to R. Kaiser; De- 
posits of nickel alloys; Nickel-bronze 247 

French process for the deposition of German silver; Watt's method . 248 
Examination of nickel baths; Method for the determination of the con- 
tent of acid , . . 249 

Methods for the examination of baths; Gravimetric analysis . . 251 

Volumetric analysis 252 

Electrolytic method of analysis 253 

Apparatus for electrolytic analysis; Washing contrivance . . . 254 
Examination of a nickel bath by electrolytic analysis .... 256 

2. DEPOSITION OF COBADT. 

Properties of cobalt; Baths for plating with cobalt .... 256 

Cobalting of copper plates for printing; Determination of the quantity 
of copper dissolved in stripping the cobalt deposit from cobalted 
copper plates 257 

Warren's cobalt solution; Cobalt solution recommended by G. W. 
Beardslee, of Brooklyn, N. Y.; Daub's bath for cobalting small fancy 
articles 258 

Cobalting by contact 259/ 

CHAPTER VIII. 

Deposition of Copper, Brass and Bronze, 
2. deposition of copper. 
Properties of copper; Copper baths, their composition, preparation, 

properties, and treatment . 261 

Hassauer's copper bath; Copper baths for iron and steel articles . .262 

Baths for coppering zinc articles . 263 

Baths prepared with cupron and copper sulphite 265 

Copper baths without potassium cyanide ; Weil's copper bath and 
method of coppering; Copper bath recommended by Walenn . . 266 



XVlll CONTENTS. 

PAGE 

Copper bath according to Pfanhauser; Gauduin's copper bath; Execu- 
tion of copper-plating 267 

Anodes used; Formation of slime on the anodes; Phenomena in baths 
containing cyanide 268 

Necessity of carefully cleaning and pickling the articles before copper- 
ing; Scratch-brushing and treatment of defective places . . . 269 

Prevention of the formation of stains; Schultz's patent to prevent the 
formation of stains; Polishing the deposit of copper . . . . 270 

Treatment of coppered articles to be coated with another metal; Cop- 
pering sheet iron or sheet zinc which is to be nickeled . . . 271 

Coppering small articles en masse ; Coppering by contact and dipping; 
To coat zinc plates with a very thin but hard layer of copper . . 272 

Bacco's copper bath; Brush coppering; Application of a thin film of 
copper to iron and steel objects; Coppering steel pens, needles' eyes, 
etc 273 

Inlaying of depressions of coppered art-castings; Examination of cop- 
per-baths containing potassium cyanide 274 

Determination of potassium cyanide ....... 275 

Determination of copper by electrolysis ....... 277 

Volumetric determination of copper ........ 278 

2. deposition of brass (Cuivre-poli Deposition). 

Constitution and varieties of brass 280 

Brass baths, their composition, preparation and treatment; Rules for 
baths containing more than one metal in solution; Brass bath accord- 
ing to Roseleur 281 

Irregular working of fresh baths; Effect of an addition of arsenious 
acid to brass baths 282 

Bath for brassing iron; Baths with cuprous sulphide .... 283 

Bath for brassing zinc; Bath for brassing cast-iron, wrought-iron and 
steel 284 

Norris and Johnson's brass bath; Solution for transferring any copper- 
zinc alloy which serves as anode; Bath for brassing all kinds of metal. 285 

Execution of brassing; On what the color of the deposit depends . . 286 

Anodes used and anode-surface required; Formation of slime on the 
anodes, and what it indicates; Remedies for the slow formation of the 
deposit 287 

Importance of the distance of the objects to be plated from the anodes; 
Brassing of unground iron castings; Brassing by contact and dipping. 289 

Examination of brass baths; Determination of free potassium cyanide 
and the content of copper; Determination of zinc by electrolysis . 2£0 

Volumetric determination of zinc 291 

3. DEPOSITION OF BRONZE. 

Gountier's solution for coating wrought- and cast-iron with bronze; 
Other bronze baths, their composition, preparation and treatment . 292 



CONTENTS. XIX 

PAGE 

Hess's bath for deposits of tombac; Execution of bronzing . . . 293 

CHAPTER IX. 
Deposition of Silver. 

Properties of silver; Statistics of the amount of silver used in electro- 
plating 294 

Silver baths, their composition, preparation and treatment; Silver bath 
for a heavy deposit of silver (plating by weight) 295 

Preparation of baths with silver chloride 296 

Preparation of baths with silver cyanide; Preparation of silver cyanide . 297 

Silver bath for ordinary electro-silvering; Treatment of silver baths — 
Silver anodes 298 

Most suitable current-strength for silver baths; Coupling of the ele- 
ments; Indication of the presence of too much, or not enough potas- 
sium cyanide 299 

The behavior and appearance of the anodes as criteria of the content of 
potassium cyanide in the bath; Keeping the bath constant by silver 
anodes 300 

Proper treatment of baths made with silver chloride; Gradual thicken- 
ing of the baths 301 

Augmentation of the content of silver in baths; Determination of the 
content in proper proportions of silver and excess of potassium cyanide. 3( ! 2 

Contrivances to keep the objects to be plated in constant agitation . 303 

Singular phenomenon in regard to silver baths ; Preparations for 
"bright-plating" 304 

Remedy against a yellow tone of the silver-plating; Areas silver-plating 
as introduced by the London Metallurgical Co. ..... 306 

Experiments in areas silver-plating ....... 307 

Execution of silver-plating; Silver-plating by weight; Mechanical and 
chemical preparation of the objects; Treatment of copper and its 
alloys 308 

Freeing from grease; Pickling; Rubbing; Pickling in the preliminary 
pickle; Amalgamating (quicking); Slinging wires .... 309 

Treatment of the objects while being being plated .... 310 

Amount of silver deposited upon various grades of plated table-ware 
manufactured by the William Rogers Manufacturing Co.; Method of 
controlling the weight of the deposit 311 

Roseleur's plating balance 312 

Plating balance together with the resistance-board, voltmeter, and 
silver bath 314 

Treatment of articles which are to retain the crystalline dead white, with 
which they come from the bath; Polishing the articles; Ordinary 
silver-plating 315 

Gore's process of silver-plating Britannia ware and articles of tin; Aus- 
tralian patent for directly silver-plating iron and steel . . .316 



XX CONTENTS. 

PAGE 

Practice of the Meriden Britannia Co. 's works at Meriden, Conn.; Treat- 
ment of Britannia or "white metal," German silver and nickel 

articles, and of steel articles 317 

Methods in use with the Wm. Rogers Manufacturing Co., Hartford, 
Conn.; For cleansing steel (cutlery); Nickel-silver (German silver) 
for spoons; Britannia metal (hollow ware); Rogers's striking solu- 
tion; Meriden Company's striking solution; Plating solution com- 
monly used by the Wm. Rogers Manufacturing Co. . . . .318 

Methods of depositing an extra heavy coating of silver on the convex 

surfaces of spoons and forks; Stopping-off and stopping-off varnish . 319 
Silvering by contact, by immersion, and cold silvering with paste; Bath 

for silvering by contact; Baths for silvering by immersion . . 320 

Preparation of solution of sodium sulphide ...... 321 

Dr. Ebermayer's silver-immersion bath; Silvering articles without the 

use of the current ... 323 

Coating small articles, such as hooks and eyes, pins, etc., with a thin 

film of silver; Cold silvering with paste 325 

Composition of argentiferous pastes; Graining 326 

Preparations used for graining 327 

Operation of graining; Resist and its composition; Gilding of grained 

watch parts 328 

Silvering of fine copper wire 329 

Imitation of niel or nielled silvering; Preparation of the nielling powder. 330 
Imitation of niel by electro-deposition; Nielling upon brass; Old 

(antique) silvering 331 

Oxidized silver; Yellow color on silvered articles 332 

Stripping silvered articles; Determination of silver-plating . . . 333 
Method for the determination of genuine silvering used by custom- 
house officers in Germany; Examination of silver baths; Determina- 
tion of free potassium cyanide ........ 334 

Determination of potassium carbonate 335 

Calculation of the quantity of barium cyanide required for the conver- 
sion of the potassium carbonate; Determination of silver by the elec- 
trolytic method 336 

Recovery of silver from old silver baths, etc. ; The wet method . . 337 
Various methods of regaining the silver 338 

CHAPTER X. 
Deposition of Gold. 

Occurrence of gold; General composition of the native metal; Proper- 
ties of gold . 340 

Shell gold or painter's gold; Gold baths, their composition, preparation 
and treatment • 341 



CONTENTS. XXI 

PAGE 

Bath for cold gilding 342 

Bath with yellow prussiate of potash for cold gilding .... 343 

Baths for hot gilding 344 

Taucher's formulae for hot gilding; Preparation of gold baths with the 

assistance of the current 345 

Management of gold baths; Use of insoluble platinum anodes and of 

steel anodes for gold baths 346 

Experiment with steel anodes 347 

Use of carbon anodes; Anodes of platinum for coloring the deposit; 

Coloration by means of the resistance-board ..... 348 

Vats for gold baths; Porcelain dish for small baths .... 349 

Execution of gold-plating; Gilding without a battery .... 350 
Preparation of the articles for gilding; Current-strength for gilding . 351 
Gilding the inner surfaces of hollow- ware; Process of gold-plating in 
the cold bath; Operations for plating with the hot bath . . . 352 

Red gilding 353 

Determination of the content of copper required for obtaining a beau- 
tiful red gold; Green gilding; Rose-color gilding; Matt gilding . 354 

Matting in the chemical or electro-chemical way 355 

Coloring of the gilding; Gilder's wax 356 

Process to give gilded articles a beautiful rich appearance; Method of 

improving bad tones of gilding 357 

Gilding metallic wire and gauze 358 

J. W. Spaeth's machine for gilding wire and gauze .... 359 

Gilding by contact, by immersion and by friction; Baths for contact 

gilding 360 

Porcelain capsules for dissolving gold ....... 361 

Preparation of " matt " for gilded articles; Baths for gilding by dipping. 363 

Gilding of porcelain, glass, etc. 365 

Gilding by friction or gilding with the rag, with the thumb, with the 

cork; Martin and Peyraud's method of gilding by friction . . . 366 
Fire or mercury gilding; Preparation of the gold amalgam; Applica- 
tion of the amalgam 367 

Method of gilding which is a combination of fire-gilding with electro- 
deposition 369 

Du Fresne's method of gilding 370 

Removing gold from gilded articles — Stripping; Determination of gen- 
uine gilding 371 

Examination of gold baths; Determination of the gold by the electro- 
lytic method; Strengthening the gold bath 372 

Recovery of gold from gold baths, etc.; The wet process . . . 373 
Recovery of gold from acid mixtures ....... 374 



XXll CONTENTS. 

PAGE 

CHAPTER XI. 
Deposition of Platinum and Palladium, 
i. deposition of platinum. 
Properties of platinum; Platinum baths, their composition, preparation 

and properties . . 375 

Bottger's bath; Preparation of platoso-ammonium chloride; Platinum 
bath patented by the Bright Platinum Plating Co., of London; Dr. 
W. H. Wahl's directions for preparing platinum baths . . . 370 

Alkaline platinate bath 377 

Preparation of an oxalate solution; Preparation of the phosphate bath. 378 

Management of platinum baths 370 

Execution of platinum-plating; Production of heavy deposits; Platiniz- 
ing glass 380 

Platinizing by contact; Recovery of platinum from platinum solutions. 381 

2. DEPOSITION OF PALLADIUM. 

Properties of palladium . . . 381 

Bertrand's palladium bath; Pillet's bath for plating watch movements. 382 

CHAPTER XII. 

Deposition of Tin, Zinc, Lead and Iron. 

i. deposition of tin. 
Properties of tin; Moire" metallique on tin; Tin baths, their composition, 
preparation and properties ......... 383; 

Direct tinniug of objects of zinc, copper and brass; Preliminary copper- 
ing of iron and steel articles; Experiments with Salzede's bronze 

bath 384 

Pfanhauser's tin bath; Taucher's tin bath 387 

Management of tin baths; Current-strength required; Anodes; Choice 

of tin salts 380 

Process of tin-plating; Tinning by contact and boiling .... 387 
Zilken's solution for tinning by contact; Tinning solutions for iron and 
steel articles, and for small brass and copper articles; Bottger's 

solution 388 

Durable coating on tin; Tinning of needles 389 

Superficial coating of tin on articles of brass, copper and iron; Stolba's 
method of tinning 390 

2. DEPOSITION OF ZINC. 

Properties of zinc ........... 390 

Zinc baths, their composition, preparation and properties . . . 391 
Anodes used in zincking .......... 392 



CONTENTS. XXI II 

PAGE 

Execution of zinc- plating; Zinc-plating of wrought-iron objects, gird- 
ers, L-iron, T-iron, etc. 393 

Profile anodes 394 

Zincking of nails, screws, etc. ; Zincking iron by contact; To coat brass 
and copper with a bright layer of zinc 395- 

Zinc alloys; Bath for depositing an alloy of zinc and tin, or of zinc, tin 
and nickel 396 

3. DEPOSITION OF LEAD. 

Properties of lead 396- 

Lead baths, their composition, preparation and properties; To coat gun 
barrels and other articles of steel and iron with superoxide of lead; 
Leading by contact; Metallic chromes (Nobili's rings, iridescent 

colors, electro-chromy) 397 

Gassiot's plan to obtain metallo-chromes 399' 

4. DEPOSITION OF IRON (STEERING). 

Principal use of the electro-deposition of iron 399- 

Iron (steel) baths, their composition, preparation and properties; Var- 

rentrapp's iron bath; Bottger's steel bath 400 

Obernetter's method of steeling copper printing plates; Production of a 

deep black deposit of iron for decorative purposes .... 401 

Management of iron baths 402. 

Advantage of steeling of printing plates over nickeling; Steeling by 

contact 40& 

CHAPTER XIII. 
Deposition of Antimony, Arsenic, Aluminium, 
i. deposition of antimony. 
Properties of antimony; Antimony baths, their composition, preparation 

and properties 404 

Schlippe's salt 405 

2. DEPOSITION OF ARSENIC. 

Properties of arsenic 405 

Arsenic baths, their composition, preparation and properties . . 406 

Deposits of antimony and arsenic by contact and immersion . . 407 

3. DEPOSITION OF ALUMINIUM. 

Properties of aluminium 407 

Aluminium baths; Bertrand's process; Goze's process; Reinbold's 

formula; New method for the electro-deposition of aluminium . 40& 
Electro-deposition upon alumininm 409- 



XXIV CONTENTS. 



Cleansing aluminium articles; Advisability of previous coppering and 
baths for that purpose; Villon's process 410 

Prof. Nees' process; Electro-deposits upon aluminium produced by the 
Mannesmann Pipe Works, Germany 411 

CHAPTER XIV. 
Galvanoplasty (Reproduction). 

Definition of galvanoplasty; Copper the most suitable metal for gal vano- 
plastic purposes; Physical properties of copper deposited by electro- 
lysis; Smee's experiments; Hiibl's experiments for the determination 
of the conditions under which deposits with different physical proper- 
ties are obtained 412 

Classes of processes used in galvanoplasty 413 

I. GALVANOPLASTIC DEPOSITION IN THE CELL- APPARATUS. 

The cell-apparatus 413 

Simple cell-apparatus for amateurs; Cell-apparatus for the production of 

cliches 414 

Large apparatus; French form of cell- apparatus 416 

German form of cell-apparatus; Copper bath for the cell- apparatus; 
Table of the approximate content of pure crystallized blue vitriol at 

different degrees Be , and 59 F 417 

Method of removing an excess of acid from the bath .... 418 

2. GALVANOPLASTIC DEPOSITION BY THE BATTERY AND DYNAMO- 

Arrangement for the employment of external sources of current; Depo- 
sitions with the battery; Coupling of elements ..... 419 
Depositions with the dynamo; Copper baths for galvanoplastic deposi- 
tions with a separate source of current 420 

Bath for depositing with the dynamo; Bath for depositing with the bat- 
tery; Solution for copper printing plates 421 

Current-density for baths at rest and when agitated; Table showing the 
results of Hiibl's experiments ........ 422 

Disadvantage of difference in composition of the upper and lower layers 
of the bath; Various methods of effecting the agitation of the bath . 423 

Anodes used for the baths 424 

Proportion of anode-surface to that of the cathodes; Examination of the 
acid copper bath; Determination of free acid; Volumetric determina- 
tion of the content of copper according to Haen's method . . . 425 

Electrolytic determination of the copper 426 

Preparation of moulds (matrices) in plastic material . . . .427 
Moulding in gutta-percha; Most simple way of softening gutta-percha. 428 

The toggle press 429 

Hydraulic press , 430 



CONTENTS. XXV 

PAGE 

Moulding in wax (stearine); Volkmer's wax mixture; Preparation of 

the wax mould; Black-leading 431 

Black-leading machines . .....'.. 432 

Silas P. Knight's process of black-leading ...... 433 

Preliminary coating of the black-leaded surface with copper; Gilt and 

silvered black-lead; Wiring the mould 434 

The building iron; The electric connection gripper; Suspension of the 

moulds in the bath 435 

Chief requisite for the production of a dense, coherent and elastic de- 
posit; Strength of the sulphuric acid for filling the clay cells . . 436 
Most suitable current-density for the production of a good deposit; 
Coupling of the elements; Controlling the current by the resistance 

board 437 

Time required for a sufficiently heavy deposit; Accumulators and their 

use 438 

Detaching the deposit or shell from the mould; Casting and melting 

table 439 

Backing the deposit or shell 440 

Finishing; The saw table; Planing or shaving machine; Mounting the 

plates . .... 443 

Process of making a copy directly from a metallic surface without the 

interposition of wax or gutta-percha 444 

Electro-etching 445 

Composition of etching ground 446 

Preparation of printing plates in relief; Heliography .... 447 

Electro-etching in steel for the production of dies for coins, reliefs, etc. 448 
Galvanoplastic reproduction of busts, vases, etc. ..... 449 

Materials for the moulds; Dissection of the objects .... 450 

Oil gutta-percha, its preparation and use ....... 451 

Metallic alloys for the preparation of moulds; Moulding with metallic 

alloys; Taking casts in plaster of Paris 452 

Moulding in plaster of Paris of large objects ...... 453 

Mode of making plaster of Paris moulds impervious to fluids . . .454 

Metallization by the wet way 455 

Parkes's method of metallization 456 

Various methods of metallization; Metallization by metallic powders . 457 
Lenoir's process — galvanoplastic method for originals in high relief; 

Gelatine moulds 458 

Brandley's directions for preparing gelatine moulds .... 459 
Special uses of galvanoplasty; Nature printing; Philipp's process for 

coating laces and tissues with copper; Production of copper tubes . 460 
Corvin's niello; Coating grasses, leaves, flowers, etc. with copper. . 461 
Plates for the production of imitations of leather; To coat wood, etc., 
with a galvanoplastic deposit of copper; To protect wooden handles 
of surgical instruments, etc., from the attacks of the acid copper bath. 462 



XXVI CONTENTS.' 

PAGE. 

Copper deposit for the mercury vessels of thermometers; Metallization 
of glass, porcelain, clay, terra cotta, etc.; Galvanoplastic deposit of 
copper on porcelain, pottery, stone-ware, etc.; Galvanoplasty in iron 

(steel) 463 

Klein's bath; Lenz's investigations 464 

Prevention of the spoiling of the deposits ...... 465 

Properties of electrolytically deposited iron; Advantages and disad- 
vantages of iron electros and of steeled copper electros . . . 466 

Galvanoplasty in silver and gold 467 

Baths for galvanoplasty in silver and in gold 46& 

CHAPTER XV. 
Coloring, Patinizing, Oxidizing, etc., of Metals — Lacquering. 

What is understood by patina and patinizing; Coloring of copper from 

the pale red of copper to a dark chestnut brown .... 469 

Brown color upon copper; Method used in the Paris Mint; Bronze-like 

color on copper 470 

Red-brown color on copper; Manduit's process of bronzing copper and 

coppered articles; Coloring copper blue black; Cuivre fume ; Black 

color upon copper; Matt-black on copper ...... 471 

Solution for obtaining a deep black color on copper and its alloys; 

Imitation of genuine patina . . 472 

Steel gray color upon copper; Coloring copper dark steel gray; Various 

colors upon massive copper and upon brass and nickel . . . 473 
Coloring of brass and bronzes; Lustrous black on brass . . . 474 

Steel gray on brass; Gray color with a bluish tint upon brass; Pale gold 

color on brass; Straw color, to brown, through golden yellow and 

tombac color on brass; A color resembling gold on brass . . . 475 
Brown color, called bronze Barb£dienne, on brass; Coloring bronze 

articles dead yellow or clay yellow to dark brown .... 476 

Smoke-bronze ; Dark red-brown color upon brass ; Coloring brass 

articles en masse brown; Violet and corn-flower blue upon brass . 477 

Spurious gilding of small silvered brass and tombac articles; Eber- 

mayer's experiments in coloring brass 478 

Coloring zinc; Experiments in coloring zinc black .... 479 

Gray, yellow, brown to black colors upon zinc; Gray coating on zinc . 480 
Bronzing on zinc; Brown patina on cast zinc; Red-brown shades on 

zinc; Yellow-brown shades on zinc; Coloring of iron; Browning of 

gun barrels 481 

Patina for protecting metals; Lustrous black on iron; Me>itens process 

for obtaining a bright black color on iron 482 

Dead black coating on clock cases of iron and steel; Durable blue on 

iron and steel; Brown-black coating with bronze lustre on iron . . 483 
To give iron a silvery appearance with high lustre; Coloring of tin; 



CONTENTS. XXV11 

PAGE 

Durable and very warm sepia brown upon tin and its alloys; Dark 
coloration on tin; Lacquering; Use of lacquers in the electro-plating 
industry 484 

Application of lacquers; Operation of gold varnishers .... 485 

Varnishes at the disposal of gold varnishers; Resinous substances and 
tinctorial matters used in the manufacture of varnishes . . . 486 

Removal of varnish from imperfectly varnished objects; Cellulose lac- 
quers and varnishes; Zapon; Kristaline 487 

Preparation of a lacquer similar to zapon or kristaline; Lacquering 
articles by dipping 488 



CHAPTER XVI. 
Hygienic Rules for the Workshop. 

Neutralization of the action of acid upon the enamel of the teeth and 
the mucous membranes of the mouth and throat; Protection against 
the corrosive effect of lime and caustic lye ...... 488 

Vessels used in the establishment not to be used for drinking purposes; 
Precautions in handling potassium cyanide and its solutions; Sensi- 
tiveness of many persons to nickel solutions; Poisoning by hydrocy- 
anic (prussic) acid, potassium cyanide and cyanides; Remedies to be 
applied 490 

Poisoning by copper salts, by lead salts, by arsenic, by alkalies, by mer- 
cury salts and sulphuretted hydrogen 491 

Poisoning by chlorine, sulphurous acid, nitrous and hyponitric gases . 492 

CHAPTER XVII. 

Chemical Products and Various Apparatus and Instruments 
Used in Electro-plating. 

a. chemical products. 

/. Acids. 

Sulphuric acid (oil of vitriol) . 493 

Recognition of sulphuric acid; Nitric acid (aqua fortis, spirit of nitre) 
and its recognition; Hydrochloric acid (muriatic acid) and its recog- 
nition; Hydrocyanic acid (prussic acid) 494 

Recognition of hydrocyanic acid; Citric acid and its recognition; Boric 
acid (boracic acid) and its recognition 495 

Arsenious acid (white arsenic, arsenic, ratsbane) and its recognition; 
Chromic acid and its recognition; Hydrofluoric acid .... 496 

Recognition of hydrofluoric acid 497 



XXV111 CONTENTS. 

PAGE 

77. Alkalies and Alkaline Earths. 

Potassium hydrate (caustic potash); Sodium hydrate (caustic soda); 

Ammonium hydrate (ammonia or spirits of hartshorn) . . . 497 
Calcium hydrate (burnt or quick lime) 498 

III. Sulphur Combinalions. 

Sulphuretted hydrogen (sulphydric acid, hydrosulphuric acid) and its 
recognition; Potassium sulphide (liver of sulphur) .... 498 

Recognition of potassium sulphide; Ammonium sulphide (sulphydrate 
or hydrosulphate of ammonia); Antimony sulphide; Black sulphide 
of antimony {stibium, sulfuraium nigrum); Red sulphide of anti- 
mony (stibium sulfuratum aurantiacum) ; Arsenic trisulphide or ar- 
senious sulphide (orpiment) 499 

Ferric sulphide 500 

IV. Chlorine Combinations. 

Sodium chloride (common salt, rock salt) and its recognition; Ammo- 
nium chloride (sal ammoniac) and its recognition; Antimony trichlor- 
ide (butter of antimony ) 500 

Arsenious chloride; Copper chloride; Tin chloride; Stannous chloride 
or tin-salt and its recognition; Stannic chloride; Zinc chloride (hy- 
drochlorate or muriate of zinc, butter of zinc) and its recognition . 501 

Nickel chloride and its recognition; Cobalt chloride acd its recogni- 
tion; Silver chloride 502 

Recognition of silver chloride; Gold chloride (terchloride of gold, mur- 
iate of gold, auric chloride) and its recognition; Platinic chloride and 
its recognition 503 

V. Cyanides. 

Potassium cyanide (white prussiate of potash) 504 

Recognition of potassium cyanide; Comparative table of potassium cya- 
nide with a different content; Copper cyanides 505 

Recognition of copper cyanides; Zinc cyanide (hydrocyanate of zinc, 
prussiate of zinc) and its recognition; Silver cyanide (prussiate or 
hydrocyanate of silver); Potassium ferro cyanide (yellow prussiate of 
potash) 506 

Recognition of potassium ferro-cyanide . . ..... 507 

VI. Carbonates. 

Potassium carbonate (potash) and its recognition; Acid potassium car- 
bonate or monopotassic carbonate, commonly called bicarbonate of 
potash; Sodium carbonate (washing soda) 507 

Sodium bicarbonate (baking powder); Calcium carbonate (marble, 
chalk); Copper carbonate and its recognition; Zinc carbonate . . 508 



CONTENTS. XXIX 



Recognition of zinc carbonate; Nickel carbonate and its recognition; 
Cobalt carbonate 509 

VII. Sulphates and Sulphites. 

Sodium sulphate (Glauber's salt); Ammonium sulphate and its recog- 
nition; Ammonium-potassium sulphate (potash-alum) . . . 509 

Recognition of ammonium-potassium sulphate; Ammonium-alum and 
its recognition; Ferrous sulphate (sulphate of iron, protosulphate of 
iron, copperas, green vitriol) and its recognition; Iron-ammonium 
sulphate; Copper sulphate (cupric sulphate, blue vitriol or blue cop- 
peras) 510 

Recognition of copper sulphate; Cuprous sulphite; Zinc sulphate (white 
vitriol) and its recognition; Nickel sulphate 511 

Recognition of nickel sulphate; Nickel-ammonium sulphate; Cobalt 
sulphate and its recognition . . . . . . . .512 

Cobalt-ammonium sulphate; Sodium sulphite and its recognition; Sod- 
ium bisulphite . . . . . . . . . . .518 

VIII. Nitrates. 

Potassium nitrate (saltpetre, nitre) and its recognition .... 513 
Sodium nitrate (cubic nitre or Chili saltpetre); Mercurous nitrate; Mer- 
curic nitrate (nitrate of mercury) and its recognition; Silver nitrate 

(lunar caustic) 514 

Recognition of silver nitrate . 515 

IX. Phosphates and Pyrophosphates. 

Sodium phosphate and its recognition; Sodium pyrophosphate and its 
recognition; Ammonium phosphate 515 

X. Salts of the Organic Acids. 

Potassium bitartrate (cream of tartar); Potassium-sodium tartrate 
(Rochelle or Seignette salt) and its recognition; Antimony-potassium 
tartrate (tartar emetic) and its recognition; Copper acetate (verdigris). 516 

I,ead acetate (sugar of lead) and its recognition; Sodium citrate . . 517 

B. VARIOUS APPARATUS AND INSTRUMENTS. 

Glass balloons and flasks; Evaporating dishes or capsules . . .517 

Glass jars; Crucibles; Hydrometers 518 

Table showing the readings of different hydrometers .... 519 

Filters 520 

Siphons 521 

Stirring rods 522 



XXX CONTENTS. 

PAGE 

APPENDIX. 
Useful Tables. 

Table of elements with their symbols, atomic weights and specific 
gravities 523 

Table of chemical and electro-chemical equivalents; Explanation of the 
table 524 

Table showing the value of equal current volumes as expressed in 
amperes per square decimetre, per square foot, and per square inch 
of electrode surface; Explanation of the table 525 

Table showing the specific electrical resistances of different sulphuric 
acid solutions at various temperatures; Table showing the specific 
electrical resistances of different copper sulphate solutions at various 
temperatures 526 

Table of the electro-motive force of elements ...... 527 

Table showing the solubility of various substances; Table showing the 
composition of the most usual alloys and solders 528 

Alloys 529 

Solders; Soft solder; Hard solder; Silver solder 530 

Gold solder; Table of the melting points of some metals; Table of high 
temperatures; Table of the specific gravity and content of solutions 
of potassium carbonate at 57.2 F. 531 

Table showing the specific gravity of sulphuric acid at 59° F. . . 532 

Table of the specific gravity and content of nitric acid; Table showing 
the specific gravity of sal ammoniac solutions at 66.2° F. . . .533 

Table showing the electrical resistance of pure copper wire of various 
diameters; Resistance and conductivity of pure copper at different 
temperatures 534 

Table showing actual diameters in decimal parts of an inch correspond- 
ing to the numbers of various wire gauges 585 

Weight of iron, copper and brass wire and plates 536 

Rules for speed; To find speed of counter-shaft in accordance with 
main shaft and machine; To find diameter of pulley on the main 
shaft; To find diameter of pulley on counter-shaft carrying belt to 
machine; To find the speed of a machine 537 

Comparison of the scales of the Fahrenheit, Centigrade and Reaumur 
thermometers, and rules for converting one scale into another . . 538 

Index 539 



ELECTRO-DEPOSITION OF METALS. 



I. 
HISTORICAL PART. 



CHAPTER I. 

HISTORICAL REVIEW OF ELECTRO-METALLURGY. 

In reviewing the history of the development of electrolysis, 
i. e., the reduction of a metal or a metallic alloy from the solu- 
tion of its salts by the electric current, the simple reduction 
which takes place by the immersion of one metal in the solu- 
tion of another, may be omitted. This mode of reduction was 
well known to the alchemist Zozimus, who described the re- 
duction of copper from its solutions by means of iron, while 
Paracelsus speaks of coating copper and iron with silver by 
simple immersion in a silver solution. 

Before the discovery, in 1789, of contact- electricity by Luigi 
Galvani, there was nothing like a scientific reduction of metal' 
by electricity; and only in 1799 did Alexander Volta, of Pavia,. 
succeed in finding the true causes of Galvani's discovery.. 
Galvani observed while dissecting a frog on a table, whereon 
stood an electric machine, that the limbs suddenly became con- 
vulsed by one of his pupils touching the crural nerve with the 
dissecting-knife at the instant of taking a spark from the con- 
ductor of the machine. The experiment was several times re- 



2 ELECTRO-DEPOSITION OF METALS. 

peated, and it was found to answer in all cases when a metallic 
conductor was connected with the nerve, but not otherwise. He 
observed that muscular contractions were produced by forming 
a connection between two different metals, one of which was 
applied to the nerve, and the other to the muscles of the leg. 
Similar phenomena having been found to arise when the leg of 
the frog was connected with the electric machine, it could 
scarcely be doubted that in both cases the muscular contrac- 
tions were produced by the same agent. From a course of 
experiments, Galvani drew the erroneous inference that these 
muscular contractions were caused by a fluid having its seat in 
the nerves, which through the metallic connections flowed over 
upon the muscles. Everywhere, in Germany, England and 
France, eminent scientists hastened to repeat Galvani's experi- 
ments, in the hope of discovering in the organism a fluid which 
they considered the vital principle ; but it was reserved to Volta 
to throw light upon the prevailing darkness. In his repeated 
experiments this eminent philosopher observed that one cir- 
cumstance had been entirely overlooked, namely, that in order 
to produce strong muscular contractions in the frog-leg experi- 
ment, it was absolutely necessary for the metallic connection to 
consist of two different metals coming in contact with each 
other. From this he drew the inference that the agent pro- 
ducing the muscular contractions was not a nerve-fluid, but was 
developed by the contact of dissimilar metals, and identical 
with the electricity of the electric machine. 

This discovery led to the construction of what is known as 
the pile of Volta, or the vjltaic pile. The same philosopher 
found that the development of electricity could be increased by 
building up in regular order a pile of pairs of plates of dissimi- 
lar metals, each pair being separated on either side from the 
adjacent pairs by pieces of moistened card-board or felt. On 
account of various defects of the voltaic pile, Crmkshank soon 
afterwards devised his well-known trough battery, which con- 
sisted of square plates of copper and zinc soldered together, 
and so arranged and fastened in parallel order in a wooden box, 



HISTORICAL REVIEW OF ELECTRO-METALLURGY. 3 

that between each pair of plates a sort of trough was formed, 
which was filled with acidulated water. 

Nicholson and Carlisle, on May 2, 1800, first decomposed 
water into hydrogen and oxygen by electrolysis; and, in 1801, 
Wollaston found that if a piece of silver in connection with a 
more positive metal, for instance, zinc, be put into copper 
solution, the silver will be coated over with copper, which 
coating will stand the operation of burnishing. 

Cruikshank, in 1 803, investigated the behavior of solutions 
of nitrate of silver, sulphate of copper, acetate of lead, and sev- 
eral other metallic salts, towards the galvanic current, and found 
that the metals were so completely reduced from their solutions 
by the current as to suggest to him the analysis of minerals by 
means of the electric current. 

To Brugnatelli we owe the first practical results in electro- 
gilding. In 1805 he gilded two silver medals by connecting 
them by means of copper wire with the negative pole of the 
pile, and allowing them to dip in a solution of fulminating gold 
in potassium cyanide, while a piece of metal was suspended in 
the solution from the positive pole. He also observed that the 
positive plate, if it consisted of an oxidizable metal, was dis- 
solved. 

One of the greatest discoveries connected with the subject, 
however, is that of Sir Humphry Davy, made October 6, 1807, 
when, by the decomposition of the alkalies by means of the 
electric current, he discovered the metals potassium and sodium. 

Prof. Oersted, of Copenhagen, in 1820, found that the mag- 
netic needle is deflected from its direction by the electric cur- 
rent. It was known long before this that powerful electric dis- 
charges affect the magnetic needle. It had, for instance, been 
observed that the needle of a ship's compass struck by light- 
ning had lost its property of indicating the North Pole, and 
several physicists, among them Franklin, had succeeded in pro- 
ducing the same phenomena by heavy discharges of the elec- 
trical machine, but they were satisfied with the supposition that 
the electric current acted mechanically, like the blow of a 



4 ELECTRO-DEPOSITION OF METALS. 

hammer. Oersted first perceived that electricity must be in a 
state of motion in order to act upon magnetism. This led to 
the construction of the galvanoscope or galvanometer, an in- 
strument which indicates whether the elements or other source 
of current furnish a current or not, and by which the intensity 
of the source of current may also to a certain degree be recog- 
nized. 

Ohm, in 1827, discovered the law named after him, that the 
strength of a continuous current is directly proportional to the 
difference of potential or electro-motive force in the circuit, and 
inversely proportioned to the resistance of the circuit. This law 
will be more fully discussed in the theoretical part. 

Ohm's discovery was succeeded, in 183 1, by the important 
discovery of electric induction by Faraday. By induction is 
understood the production of an electric current in a closed 
circuit which is in the immediate neighborhood of a current- 
carrying wire. Faraday further found that the current induced 
in the neighboring wire is not constant, because after a few 
oscillations the magnetic needle returned to the position 
occupied by it before a current was passed through the 
current- carrying wire ; whilst, when the current was broken, the 
needle deflected in the opposite direction. 

In the year following the discovery of Faraday, Pixii, of 
Paris, constructed the first electro-magnetic induction machine. 

Faraday's electrolytic law of the proportionality of the cur- 
rent-strength and its chemical action, and that the quantities of 
the various substances which are reduced from their combina- 
tions by the same current are proportional to their chemical 
equivalents, was laid down and proved in 1833, and upon this 
Faraday based the measurement of the current-strength by 
chemical deposition, as, for instance, that of water, in the 
voltmeter. 

Of the practical electro-chemical discoveries there remain to 
be mentioned the production of iridescent colors, in 1826, by 
Nobili, and the production of the amalgams of potassium and 
sodium, in 1853, by Bird. 



HISTORICAL REVIEW OF ELECTRO-METALLURGY. 5 

The actual galvanoplastic process, however, dates from 1838. 
In the spring of that year Prof. Jacoby announced to the 
Academy of Sciences of St. Petersburg, a description of his 
discovery of the utility of galvanic electricity as a means of re- 
producing objects of metal. Hence Jacoby must be considered 
the father of galvanoplasty in as far as he was the first to utilize 
and give practical form to the discoveries made up to that time. 
Though Jacoby's process was published in the English periodi- 
cal, " The Athenaeum," of May 4, 1839, Mr. T. Spencer, who 
read a paper on the same subject, September 13, 1839, before 
the Liverpool Polytechnic Society, claimed priority of inven- 
tion, as was also done by Mr. C. J. Jordan, who, on May 22, 
1839, sent a letter to the "London Mechanical Magazine," 
which was published on June 8, 1839. 

From this time forward the galvanoplastic art made rapid 
progress, and by the skill and enterprise of such men as the 
Elkingtons, of Birmingham, and De Ruolz, of Paris, it was 
speedily added to the industrial arts. 

Though copies of a metallic object by means of galvanoplasty 
could now be made, the employment of the process was re- 
stricted to metallic objects of a form suitable for the purpose, 
until, in 1840, Murray succeeded in making non-metallic sur- 
faces conductive by the application of graphite (black lead, 
plumbago), which rendered the production of galvanoplastic 
copies of wood-cuts, plaster-of-Paris casts, etc., possible. 

Dr. Montgomery, in 1843, sent to England samples of gutta- 
percha, which was soon found to be a suitable material for the 
production of negatives of the original models to be reproduced 
by galvanoplasty. 

Though it was now understood how to produce heavy de- 
posits of copper, those of gold and silver could only be obtained 
in very thin layers. Scheele's observations on the solubility of 
the cyanide combinations of gold and silver in potassium 
cyanide, led Wright, a co-worker of the Elkingtons, to employ, 
in ] 840, such solutions for the deposition of gold and silver, 
and it was found that deposits produced from these solutions 



6 ELECTRO-DEPOSITION OF METALS. 

could be developed to any desired thickness. The use of solu- 
tions of metallic cyanides in potassium cyanide prevails at the 
present time, and the results obtained thereby have not been 
surpassed by any other practice. 

From the same year also dates the patent for the deposition 
of nickel from solution of nitrate of nickel, which, however, did 
not attract any special attention. This may have been chiefly 
due to the fact that the deposition of nickel from its nitrate 
solution is the most imperfect and the least suitable for the 
practice. 

To Mr. Alfred Smee we owe many discoveries in the deposi- 
tion of antimony, platinum, gold, silver, iron, lead, copper, and 
zinc. In publishing his experiments, in 184 1, he originated 
the very appropriate term " electro-metallurgy " for the process 
of working in metals by means of electrolysis. 

Prof. Boettger, in 1842, pointed out that dense and lustrous 
depositions of nickel could be obtained from its double salt, 
sulphate of nickel with sulphate of ammonium, as well as from 
ammoniacal solution of sulphate of nickel; and that such de- 
posits, on account of their slight oxidability, great hardness, 
and elegant appearance, were capable of many applications. 
However, Bcettger's statements fell into oblivion, and only in 
later years, when the execution of nickeling was practically 
taken up in the United States, his labors in this department 
were remembered in Germany. To Boettger we are also in- 
debted for directions for coating metals with iron, cobalt, 
platinum, and various patinas. 

In the same year, De Ruolz first succeeded in depositing 
metallic alloys — for instance, brass — from the solutions of the 
mixed metallic salts. In 1843, the first use of thermo-electricity 
appears to have been made by Moses Poole, who took out a 
patent for the use of a thermo-electric pile instead of a voltaic 
battery for depositing purposes. 

From this time forward innumerable improvements in exist- 
ing processes were made ; and also the first endeavors to apply 
Faraday's discoveries to practical purposes. 



HISTORICAL REVIEW OF ELECTRO-METALLURGY. J 

The invention of depositing metals by means of a permanent 
current of electricity obtained from steel magnets was perfected 
and first successfully worked by Messrs. Prime & Son, at their 
large silverware works, Birmingham, England, and the original 
machine, constructed by Woolrych in 1844 — tne fi rst magnetic 
machine that ever deposited silver on a practical scale — is still 
preserved at their works in its original position as a valuable 



Fig. 1. 




and interesting relic. The Woolrych machine stands 5 feet 
high, 5 feet long, and 2]/ 2 feet wide. An illustration of this 
original electro-plating machine, kindly furnished us by the 
Hanson & Van Winkle Co., of Newark, N. J., is given in Fig. 1. 
As early as 1854, Christofle & Co. endeavored to replace 
their batteries by magneto-electrical machines, and used the 
Holmes type, better known as the Alliance Machine, which, how- 



8 ELECTRO-DEPOSITION OF METALS. 

ever, did not prove satisfactory ; and besides, the prices of these 
machines were, in comparison with their efficacy, exorbitant. 
The machine constructed by Wilde proved objectionable on 
account of its heating while working, and the consequent fre- 
quent interruptions in the operations. 

In i860 Dr. Antonie Pacinotti, of Pisa, suggested the use of 
an iron ring wound around with insulated wire, in place of the 
cylinder. This ring, named after its inventor, has, with more or 
less modifications, become typical of many machines of modern 
construction. In the construction of all older machines, steel 
magnets had been used, and their magnetism not being con- 
stant, the effect of the machine was consequently also not 
constant. Furthermore, they generated alternately negative 
and positive currents, which, by means of commutators, had to 
be converted into currents of the same direction ; and this, in 
consequence of the vigorous formation of sparks, caused the 
rapid wearing out of the commutators. 

These defects led to the employment of continuous mag- 
netism in the iron cores of the electro-magnets, the first 
machine based upon this principle being introduced in 1866, 
by Siemens, which, in 1867, was succeeded by Wheatstone's. 

However, the first useful machine was introduced in 1871, 
by Zenobe Gramme, who in its construction made use of Paci- 
notti's ring. This machine was, in 1872, succeeded by Hefner- 
Alteneck's, of Berlin. In both machines the poles of the elec- 
tro-magnet exert an inducing action only upon the outer wire 
wrappings of the revolving ring, the other portions being 
scarcely utilized, which increases the resistance and causes a 
useless production of heat. This defect led to the construction 
of flat-ring machines, in which the cylindrical ring is replaced 
by one of a flat shape, and of a larger diameter, thus permitting 
the induction of both flat sides. Such a machine was, in 1884, 
built by Siemens & Halske, of Berlin ; and in the same year by 
S. Schuckert, of Nurenberg. In Schuckert's modern machines 
nearly three-quarters of all the wire wrappings are under the 
inducing influence of both of the large pole shoes of the electro- 
magnets. 



HISTORICAL REVIEW OF ELECTRO-METALLURGY. 9 

Of European constructions of dynamo-electrical machines 
may be mentioned Mather's, Elmore's, Fein's, Krottlinger's> 
Naglo's, Reutlinger's, Lahmeyer's, Poschmann & Co., and Dr* 
G. Langbein & Co.'s. In this country Weston's machine and 
the dynamos manufactured by the Hanson & Van Winkle Co., 
of Newark, N. J., the Zucker & Levett Chemical Co., of New 
York, and others are largely used for electro-plating purposes. 

For the sake of completeness, there may be mentioned the 
investigators and practitioners who during the last twenty years 
have contributed much to the improvement of the electro- 
chemical processes and the perfection of galvanoplasty. Be- 
sides those already named, they are : Elkington, Becquerel, 
Heeren, Roseleur, Eisner, von Leuchtenberg, Meidinger, Weil, 
Goode. Christofle, Klein, von Kress, Thompson, Adams, GaifTe 
and others. 



II. 

THEORETICAL PART. 



CHAPTER II. 



MAGNETISM AND ELECTRICITY 



i. Magnetism. 



For the better understanding of the electrolytic laws it will 
be necessary to commence with the phenomena presented by 
magnetism, and to consider them somewhat more closely. 

A particular species of iron ore is remarkable for its property 
of attracting small pieces of iron and causing them to adhere to 
its surface. This iron ore is a combination of ferric oxide with 
ferrous oxide (Fe 3 4 ), and is called loadstone or magnetic iron 
ore. Its properties were known to the ancients, who called it 
magnesian stone, after Magnesia, a city in Thessaly, in the 
neighborhood of which it was found. If a natural loadstone be 
rubbed over a bar of steel, its characteristic properties will be 
communicated to the bar, which will then be found to attract 
iron filings like the loadstone itself. The bar of steel thus 
treated is said to be magnetized, or to constitute an artificial 
magnet. The artificial magnets thus produced may be straight, 
in the shape of a horse-shoe, or annular; but no matter what 
their form may be, there will always be two regions where the 
attractive force reaches its maximum, while between these two 
points there is a region which has no attractive effect whatever 
upon iron filings. As a rule, the two ends of the magnet show 
the greatest attractive force, and they are called the magnetic 

( io) 



MAGNETISM AND ELECTRICITY. I I 

poles, whilst the line running around the magnet, which pos- 
sesses no attractive force, is termed the neutral line or neutral 
zone. In a closed magnet the poles are situated on the ends of 
one and the same diameter, while the neutral zones are located 
on the ends of a diameter standing perpendicular to the first. 

When a magnetized bar or natural magnet is suspended at 
its centre in any convenient manner, so as to be free to move 
in a horizontal plane, it is always found to assume a particular 
direction with regard to the earth, one end pointing nearly 
north and the other nearly south. If the bar be removed from 
this position it will tend to reassume it, and after a few oscilla- 
tions, settle at rest as before. The direction of the magnetic 
bar, i. e., that of its longitudinal axis, is called the magnetic 
meridian, while the pole pointing towards the north is usually 
distinguished as the north pole of the bar, and that which points 
southward as the south pole. 

A magnet, either natural or artificial, of symmetrical form, 
suspended in the presence of a second magnet, serves to ex- 
hibit certain phenomena of attraction and repulsion, which 
deserve particular attention. When a north pole is presented to 
a south pole, or a south pole to a north pole, attraction ensues 
between them, the ends of the bar approaching each other, and, 
if permitted, adhering with considerable force. When, on the 
other hand, a north pole is brought near a second north pole, 
or a south pole near another south pole, mutual repulsion is 
observed, and the ends of the bar recede from each other as 
far as possible. Poles of an opposite name attract, and poles of 
a similar name repel each other. 

According to the theory or hypothesis proposed by Ampere, 
magnetism is caused by the presence of electric currents in the 
ultimate particles of matter. This theory assumes — 

1. That the ultimate particles of all magnetizable bodies 
have closed electric circuits in which electric currents are con- 
tinually flowing. 

2. That in an unmagnetized body these circuits neutralize 
one another, because they have different directions. 



12 ELECTRO-DEPOSITION OF METALS. 

3. That the act of magnetization consists in such a polariza- 
tion of the particles as will cause these currents to flow in 
one and the same direction, magnetic saturation being reached 
when all the separate circuits are parallel to one another. 

4. That coercive force is due to the resistance these circuits 
offer to a change in the direction of their planes. 

Guided by these considerations, Ampere produced a coil of 
wire, called a solenoid, which is the equivalent of the magnetiz- 
ing circuit assumed by his theory. It therefore follows that an 
electric current sent through a coil of insulated wire surround- 
ing a rod or bar of soft iron, or other readily magnetizable 
material, will make it a magnet. A magnet so produced is 
called an electro-magnet; the magnetizing coil is called a 
helix, or solenoid. The polarity of the magnet depends on 
the direction of the current, or on the direction of winding of 
the helix or solenoid. The improbability of an electric cur- 
rent continually flowing in a circuit without the expenditure 
of energy, has led many scientific men to reject Ampere's 
theory of magnetism. 

If an iron or steel needle be suspended free in the neighbor- 
hood of a magnet, it assumes a determined direction according 
to its greater or smaller distance from the poles or from the 
neutral zone. However, before the needle assumes this direc- 
tion it swings rapidly with a shorter stroke, or slowly with a 
longer stroke, according to the greater or smaller attractive 
force exerted upon it. The space within which the magnetic 
action of a magnet is exercised is called the magnetic field, 
and the magnetic, as well as the electric, attractions and repul- 
sions are, according to Coulomb, as the densities of the fluids 
acting upon each other, and inversely as the square of their 
distance. 

2. Electricity. 

In an ordinary state solid bodies exhibit no attractive effect 
upon small light particles, such as strips of paper, balls of elder- 
pith, etc. ; but many solid bodies on being rubbed with a piece 
of dry cloth or fur acquire the property of attracting such light 



MAGNETISM AND ELECTRICITY. 1 3 

bodies as mentioned above. The cause of this phenomenon is 
called electricity, and the bodies which possess this property of 
becoming electric by friction are termed idio- electrics, and those 
which do not appear to possess it, non-electrics. Gray, in 1727, 
found that all non-electric bodies conduct electricity, and hence 
are conductors, while those which become electric by friction 
are non-conductors of electricity. Strictly speaking, there are 
no non conductors, because the resins, silk, glass, etc., conduct 
electricity, though only very slightly. It is therefore better to 
distinguish good and bad conductors. To test whether a body 
belongs to the idio-electrics, the so called electroscope is used, 
which in its simplest form consists of a glass rod mounted on a 
stand, and bent at the top into a hook, from which hangs by a 
silken thread or hair a pith ball. If, on bringing the rubbed 
body near the pith ball, the latter is attracted, the body is elec- 
tric ; whilst if the ball is not attracted, the body is either non- 
electric or its electricity is too slight to produce an attractive 
effect. 

From the following experiments it was found that there exist 
two kinds of electricity : When a rubbed rod of glass or shellac 
is brought near the ball of elder-pith suspended to a silk thread, 
the ball is attracted, touches the rod, adheres for a few moments 
and is then repulsed. This repulsion is due to the fact that the 
ball by coming in contact with the rod becomes itself electric, 
and its electricity must first be withdrawn by touching with the 
hand before it can again be attracted by the rod. By now 
taking two such balls, one of which has been made electric by 
touching with a glass rod, which had been rubbed with silk, 
and the other by touching with a shellac rod rubbed with cloth, 
it will be observed that the ball, which is repulsed by the glass 
rod, is attracted by the shellac rod, and vice versa. These two 
kinds of electricity are called vitreous or positive, and^resinous 
or negative electricity, and it has been found that electricities of 
a similar name attract, and electricities of an opposite name re- 
pel each other. 

For want of a concrete knowledge of the electric agent which 



14 ELECTRO-DEPOSITION OF METALS. 

produces the electric phenomena, various theories or hypotheses 
have been advanced to explain these phenomena and the action 
of the electric forces. Only two of the best known theories or 
hypotheses shall here be mentioned. 

Double fluid hypothesis of electricity. By this hypothesis it 
is endeavored to explain the causes of electric phenomena by 
the assumption of the existence of two different electric fluids. 

The double fluid hypothesis assumes: — 

1 . That the phenomena of electricity are due to two tenuous 
and imponderable fluids, the positive and the negative. 

2. That the particles of the positive fluid repel one another, 
as do also the particles of the negative fluid; but that the par- 
ticles of the positive fluid attract the particles of the negative, 
and vice versa. 

3. That the two fluids are strongly attracted by matter, and 
when present in it produce electrification. 

4. That the two fluids attract one another and unite, thus 
masking the properties of each. 

5. That the act of friction separates these fluids, one going 
to the rubber and the other to the thing rubbed. 

Single fluid hypothesis of electricity. By this hypothesis it is 
endeavored to explain the cause of electric phenomena by the 
assumption of the existence of a single electric fluid. 

The single fluid hypothesis assumes: — 

1. That the phenomena of electricity are due to the presence 
of a single, tenuous, imponderable fluid. 

2. That the particles of this fluid mutually repel one another, 
but are attracted by all matter. 

3. That every substance possesses a definite capacity for 
holding the assumed electric fluid, and that when this capacity 
is just satisfied, no effects of electrification are manifest. 

4. That when the body has less than this quantity present, it 
becomes negatively excited, and when it has more, positively 
excited. 

5. That the act of friction causes a redistribution of the fluid, 
part of it going to one of the bodies, giving it a surplus, thus 



MAGNETISM AND ELECTRICITY. I 5 

positively electrifying it, and leaving the other with a deficit, 
thus negatively electrifying it. 

However, the epoch-making investigations of Prof. Herz, of 
Bonn (1889), have led to different views regarding the nature 
of electricity. Herz has shown by experiments that electricity 
is transmitted in space by waves, like heat and light, and he has 
determined the length and velocity of electrical waves. From 
this it has been ascertained that electricity is founded upon 
motion, and that the current appearing in a conductor has to 
be referred to vibrations of the molecules forming the conduc- 
tor, relatively to vibrations of the ether enveloping the mole- 
cules. By the term ether is designated the imponderable 
medium pervading all space. Hence electricity is an energy, 
just the same as light and heat are manifestations of energy. 

According to Coulomb, the electric attractions and repulsions 
are as the densities of the fluids acting upon each other, and in- 
versely as the square of the distance. 

However, a current of electricity is created not only by fric- 
tion, but also by the contact of various metals. In the same 
manner as the copper and iron in Galvani's experiments with 
the frog-leg, other metals and conductors of electricity also be- 
come electric by contact, the electric charges being, however, 
stronger or weaker, according to the nature of the metals. If 
zinc be brought in contact with platinum, it becomes more 
strongly positively electric than when in contact with copper ; 
whilst, however, copper in contact with zinc is negatively ex- 
cited, in contact with platinum it becomes positively electric. 
By now arranging the metals in a series, so that each preceding 
metal becomes positively electric in contact with the succeed- 
ing one, a series of electro-motive force or tension is obtained, in 
which the metals or conductors of electricity stand as follows : 

-f- Zinc, cadium, tin, iron, lead, copper, nickel, 
Silver, antimony, gold, platinum, carbon — . 

While two metals of the series of electro -motive force or tension 
touching each other become electrically excited in such a manner 



1 6 ELECTRO-DEPOSITION OF METALS. 

that one becomes positively and the other negatively electric, an 
exchange of the opposite electricities takes place by introducing 
a conducting fluid between the metals. Thus, if a plate of zinc 
and a plate of copper connected by a metallic wire are immersed 
in a conducting fluid, for instance, dilute sulphuric acid, the 
electricity of the positive zinc passes through the fluid to the 
negative copper, and returns through the wire — the closed circuit 
— to the zinc. However, in the same degree with which the 
electricities equalize themselves, new quantities of them are 
constantly formed on the points of contact of the metals with 
the conducting fluid ; and, hence, the flow of electricity is con- 
tinuous. This electric current generated by the contact of 
metals and fluids is called the galvanic current ; or, since it is 
generated by the intervention of fluid conductors, hydro- electric 
current. A combination of conductors which yields such a 
galvanic current, is called a galvanic element or galvanic chain. 

It would here be the place to discuss the various galvanic 
elements, but it is thought better to describe them in a sepa- 
rate chapter, and first to explain the laws and the actions of 
the galvanic current. 

Electrical potential. — The property of electricity correspond- 
ing to head or pressure, as applied in speaking of gas or water- 
power, is termed the electrical potential. Two bodies have the 
same electrical potential when, connected by a metallic wire, 
they develop no electricity. 

Electro-motive force. — If, however, two bodies connected by 
a metallic wire possess unequal electrical potentials, a move- 
ment of the electricty takes place, and the force which produces 
this movement or current is called the electro-motive force or 
tension. It, therefore, corresponds to the difference of the 
potentials ; and the magnitude of this difference of the poten- 
tials is the measure for the electro-motive force. 

Resistance. — All conductors offer a certain amount of resist- 
ance to the forward movement of the electric current. By con- 
necting, for instance, two bodies charged with electricity and 
possessing a difference of potentials, by a metallic conductor, a 



MAGNETISM AND ELECTRICITY. 1 7 

certain time is required for the compensation of the difference 
of potentials, or, in other words, before the electrical equilib- 
rium is established. By now keeping the difference of poten- 
tials constant, the quantity of electricity which passes through 
the closed conductor — the closed circuit — depends on the 
resistance which the latter offers to the passage of the current. 

The resistance of a conductor is proportional to its length and 
inversely to its cross-section and its conducting capacity ; i. e., the 
longer the conducting circuit the greater the resistance, and the 
greater its cross-section the smaller the resistance. Wires of 
small diameter will, therefore, offer greater resistance to the 
current thau those with larger diameter, and wires with good 
conducting capacity will produce less resistance than those 
with poor conducting capacity. According to Lazarus Weiler, 
the conducting power of metals is in declining order as fol- 
lows : Silver, chemically pure copper, gold, silicon bronze, 
commercial copper, aluminium, zinc, brass, tin, steel, platinum, 
lead, nickel, antimony. 

Quantity of current. Ohm's law. — The quantity of electricity, 
or, in other words, the current strength, which an element fur- 
nishes at a determined extreme point, depends on the strength 
of the electro- motive force which impels the current, as well as 
on the resistance which the conductor offers to the current. In 
the preceding it has been seen that the electro-motive force 
corresponds to the difference of the potentials of two conductors 
connected by a metallic wire ; the greater this difference is, the 
greater the energy with which the compensation of the elec- 
tricities takes place. It has also been explained that the re- 
sistance increases in proportion to the length, and decreases 
with the increase in the cross-section of the conductor. Upon 
these relations Ohm's law is based, and in its completeness it 
maybe summed up as follows: The quantity of electricity or 
the strength < ifitensity ) of current is directly proportional to the 
sum of the electro- motive forces of the exciting elements ', and is 
inversely proportional to the sum of the resistances of its closed 
circuit ; however, the resistance of each part of the closed circuit 

2 



1 8 ELECTRO-DEPOSITION OF METALS. 

is proportional to its length and inversely proportional to its cross- 
section. Now, if 5 indicates the strength of current, E the sum 
of the electro-motive forces, and L the total resistance, then 
the strength of current 5 is — 

z 

The total resistance L is, however, composed of two different 
resistances, namely, of the so-called essential or internal resist- 
ance, which expresses the resistance of the substances in the 
elements themselves, and of the non-essential or external resist- 
ance of the closed circuit. If, therefore, the internal resistance 
= R and the external resistance = r, the total resistance will 
be L = R + r } and the formula given above is changed to 

* = _-*_. 
R + r 

Let us now examine the useful applications which result from 
Ohm's law, to the coupling of the elements, they being of great 
importance to the practical electro-plater. According to the 
above formula, which expresses the total performance of a bat- 
tery, the strength of current of a single element is, if s indicates 
its current strength, e the electro-motive force, R the essential 
or internal resistance, and r the resistance in the closed circuit, 



R + r 

By now uniting several such elements, let us say n elements, 
to a column, the electro-motive force of the latter has become 
n J re = ne, and the internal resistance nr. With the same 
closed circuit as that of the single element, r will not increase, 
hence the strength of these n elements must be written — 



n R + r 

It is now clear that when a determined closed circuit of the 
resistance r is given, the strength of current cannot be in- 
definitely augmented by increasing the number of n elements; 
because, though the electro-motive force, by the augmentation 



MAGNETISM AND ELECTRICITY. 1 9 

of n elements, increases by so many n, the internal resistance R 
also grows, so that finally the value r, which remains constant, 
disappears, contrary to the resistance R, which increases n 
times. Hence, the strength of current constantly approaches 
more the limit of value — 

n e e , 

On the other hand, the effect can neither be increased by 
enlarging the area of the pair of plates nor by decreasing the 
resistance of the fluid in a given number of elements. Because 
when r, the external resistance, is sufficiently large so that the 
internal resistance, n R, may be neglected, the intensity always 

approaches more the value — . 

r 

Hence, it follows that the augmentation of the area of the ex- 
citing pair of plates produces an increase in the current- strength 
only when the external resistance in the closed circuit is small 
in proportion to the internal resistance of the battery. 

If we now apply the results of the above explanations to 
practice, we find that the elements may be coupled in various 
ways according to requirement. 

i. If, for instance, four Bunsen elements (carbon-zinc) are 
coupled one after another in such a manner that the zinc of one 
element is connected with the carbon of the next, and so on 

Fig. 2. 

(Fig. 2), the current passes four times in succession through 
an equally large layer of fluid, in consequence of which the in- 
ternal resistance, 4 R, is four times greater than that of a single 
element, while the resistance of the closed circuit, r, remains 
the same. Hence, while the current- strength is thereby not in- 
creased, the electro-motive force is, and for this reason this 



20 



ELECTRO-DEPOSITION OF METALS. 



mode of coupling is called the union or coupling of the elements 
for electro-motive force or tension. 

2. By connecting four elements alongside of each other, i. e. y 
all the zinc plates and all the carbon plates one with another 

Fig. 3. 




Fig. 4. 



(Fig. 3), the current simultaneously passes through the same 
layer of fluid in four places ; the internal resistance of the bat- 
tery is therefore the same as that of a single element, and since 
the area of the plates is four times larger than that of a single 
element, the quantity of current is aug- 
mented by this mode of coupling. 
This is called coupling for quantity of 
current. 

3. Two elements may, however, be 
connected for electro-motive force or 
tension, and several such groups 
coupled alongside of each other as 
shown in Fig. 4, whereby, according to 
what has above been said, the electro- 
motive force as well as the current 
strength is augmented. This mode of 
connection is called mixed coupling. 

According to the resistance of the bath, as well as of the ex- 
terior closed circuit, and the surfaces to be plated, the electro- 
plater may couple his elements in either way, and in speaking 
later on of the elements the various modes of coupling will be 
further discussed. We will here only mention the proposition 
deduced from Ohm's law, that a number of galvanic elements 
yield the maximum of intensity of current when they are so 
arranged that the internal resistance of the battery is equal to the 




MAGNETISM AND ELECTRICITY. 21 

resistance in the closed circuit. Hence, when operating with 
baths of good conductivity and slight resistance, for instance 
acid copper baths, silver cyanide baths, etc., with a slight dis- 
tance between the anodes and the objects, and with a large 
anode-surface, it will be advantageous to couple the elements 
alongside of each other for quantity. However, for baths with 
greater resistance and with a greater distance of the anodes 
from the objects, and with a smaller anode surface, it is best to 
couple the elements one after the other for electro-motive force or 
tension. 

The effects of the electric current are thermal, physiological, 
electro-magnetic, inductive, and chemical ; however, for our 
purposes, only the last three need be discussed. 

Electro- magnetism. 

If a wire conveying the electric current be brought near a 
magnetic needle, the latter will immediately be deflected from 
its direction, no matter whether the wire conveying the current 
be placed alongside, above, or beneath the magnetic needle. 
The direction which the needle will assume when placed in any 
particular position to the conducting wire, may be determined 
by the following rule : Let the current be supposed to pass 
through a watch from the face to the back : the motion of the 
north pole will be in the direction of the hands. Or, let the ob- 
server imagine himself swimming in the direction of the current 
with his face towards the needle : the north pole of the needle 
will then be deflected towards his left hand. 

When the needle is subjected to the action of two currents in 
opposite directions, the one above and the other below, they 
will obviously concur in their effects. The same thing happens 
when the wire carrying the current is bent upon itself and the 
needle placed between the two portions ; and since every time 
the bending is repeated a fresh portion of the current is made 
to act in the same manner upon the needle, it is easy to see how 
a current, too feeble to produce any effect when a simple straight 
wire is employed, may be made by this contrivance to exhibit 



22 ELECTRO-DEPOSITION OF METALS. 

a powerful action on the magnet. It is on this principle that 
instruments called galvanoscopes, galvanometers, or multipliers 
are constructed. They serve not only to indicate the existence 
of electrical currents, but also to show by the effects upon the 
needle the direction in which they are moving. The delicacy of 
the instrument has been increased by Nobili through the use of 
a very long coil of wire, and by the addition of a second needle. 
This instrument is known as the astatic galvanometer. The two 
needles are of equal size and magnetized as nearly as possible 
to the same extent. They are then immovably fixed together 
parallel and with their poles opposed, and hung by a long fibre 
of untwisted silk, with the lower needle in the coil and the Upper 
one above it. The advantage thus gained is twofold : The sys- 
tem is astatic, unaffected, or nearly so, by the magnetism of the 
earth ; and the needles being both acted upon in the same 
manner by the current, are urged with much greater force than 
one alone would be, all the actions of every part of the coil 
being strictly concurrent. A divided circle is placed below the 
upper needle, by which the angular motion can be measured, 
and the whole is inclosed in glass, to shield the needles from 
the agitation of the air. 

The deflection of the magnetic needle by the electric current 
has led to the construction of instruments which allow of the 
intensity of the current being measured by the magnitude of 
the deflection. Such instruments are, for instance, the tangent 
galvanometer, the sine galvanometer, etc., but they are almost 
exclusively used for scientific measurements, while for the de- 
termination of the intensity of current for electro-plating pur- 
poses other instruments are employed, which will be described 
later on. However, the electric current exerts not only a re- 
flecting action on magnetic needles, but is also capable of pro- 
ducing a magnetizing effect on iron and steel. If a bar of iron 
be surrounded by a coil of wire, covered with silk or cotton for 
the purpose of insulation, it becomes magnetic so long as the 
current is conducted through the coil. Such iron bars con- 
verted into temporary magnets by the action of the current are 



MAGNETISM AND ELECTRICITY. 23 

called electro-magnets, and they will be more highly magnetic 
the greater the number of turns of the coil, and the more in- 
tense is the current passing through the turns. 

However, not only the iron bar, around which the current 
circulates, becomes magnetic, but also a conducting wire 
through which passes a strong current. By suspending a cir- 
cular conducting wire so that it is free to move around its ver- 
tical axis, its direction is affected by the magnetism of the 
earth, and it will take up a position so that its plane stands at 
a right angle to the plane of the magnetic meridian. By now 
conducting the current through a wire having the form of a 
long helix, a so-called solenoid, the wire will, in a like manner, 
place itself with the turns of the helix at right angles to the 
plane of the magnetic meridian, or, in other words, the axis of 
the solenoid will lie in the magnetic meridian. 

In the same manner as an electrified conducting wire acts 
upon a magnet, two electrified wires exert an attracting and re- 
pelling influence on each other, the general law of the action 
being that electric currents moving in parallel lines attract one 
another if they move in the same direction, and repel one another 
if they move in opposite directions. 

Induction. 

By induction is understood the production of an electric cur- 
rent in a closed circuit which is in the immediate neighborhood 
of a current-carrying wire. 

Suppose we have two insulated copper wire spirals, A and B 
(Fig. 5 ), B being of smaller diameter and inserted in A. When 
the two ends of B are connected with the poles of a bat- 
tery a current is formed in A the moment the current of B is 
closed. This current is recorded by the deflection of the mag- 
netic needle of a multiplier, M, which is connected with the ends 
of A, the deflection of the needle showing that the current pro- 
duced in A by the current in B moves in an opposite direction. 
The current in A, however, is not lasting, because, after a few 
oscillations, the magnetic needle of the multiplier returns to its 



24 



ELECTRO-DEPOSITION OF METALS. 



previous position and remains there, no matter how long the 
current may pass through B. If, however, the current in B be 
interrupted, the magnetic needle swings to the opposite direc- 
tion, thus indicating the formation of a current in A, which 
passes through it in the same direction as the interrupted 
current in B. 

The current causing this phenomenon is called the primary 
or inductive current, and that produced by it in the closed cir- 
cuit the secondary, induced or induction current. From what 
has been above said, it is clear that an electric current at the 



Fig. 5. 




moment of its formation induces in a neighboring closed circuit 
a current of opposite direction, but when interrupted, a current 
of the same direction. 

In the same manner as closing and opening the inductive 
current, its sudden augmentation also effects the induction of a 
current of opposite direction in a neighboring wire, while its 
sudden weakening induces a current of the same direction ; the 
same effect being also produced by bringing the inductive wire 
closer to, or removing it further from, the neighboring wire. 
The induced currents being alternately formed by opening and 



MAGNETISM AND ELECTRICITY. 25 

closing the circuit, and they showing different directions, the 
term alternating currents has been applied to them. 

If the windings of the spirals are very close together, each 
winding induces the other, the so-called extra currents being 
thereby formed. 

The induced currents follow Ohm's law the same as the in- 
ductive current. A long inducing wire with a small cross-sec- 
tion offers greater resistance than a short wire with a larger 
cross-section, and consequently in the first case the current 
will possess slighter intensity and higher tension, and in the 
other greater intensity and less tension. 

In the same manner as an electrified wire induces a current 
in a neighboring wire, a magnet or electro-magnet also pro- 
duces induced currents in a coil of wire surrounding it. These 
currents act in the same manner as those produced by other 
means, and by taking into consideration Ohm's law, currents 
of great and slight intensity can be produced at will, as will be 
seen in speaking of the dynamo-electric machines, the con- 
struction of which is based upon the principle of induction. 

Chemical actions of the electrical current — Electrolysis. 

An electric current on being conducted through a fluid effects 
the reduction of its constituents. By cutting, for instance, the 
conductor of an electric current, and introducing the two wire 
ends thereby formed into water acidulated with dilute sulphuric 
acid, the water, provided the current is strong enough, is de- 
composed into its constituents, hydrogen and oxygen, the 
former separating in the form of gas on the negative pole and 
the latter on the positive. If such a decomposition does not 
take place, the fluid does not conduct the current. Pure water 
by itself is a bad conductor, and to make its decomposition 
possible it has to be made conductive by acidulation with dilute 
sulphuric acid. When a chemical composition is decomposed 
by the current, the constituent forming the basis of the com- 
bination separates on the negative pole, and that constituting 
the acid on the positive ; hence metals and hydrogen are lib- 



2 6 ELECTRO-DEPOSITION OF METALS. 

erated on the negative, and acids and oxygen on the positive, 
pole. To Faraday is due the discovery of the chemical actions 
of the current and the exposition of the laws governing the 
separation of the constituents. He adopted the term electrolysis 
for the electrical separation of chemical combinations, and 
electrolyte for the fluids subjected to electrical decomposition. 
To the poles or plates leading the current into and out of the 
electrolyte he applied the term electrodes, the positive pole 
being the anode, and the negative pole the cathode. The ele- 
ments of the electrolyzed liquid, which are liberated by the 
action of the current, are termed ions, those set free on the 
anode or positive electrode bemg termed anions, and those at 
the cathode or negative anode kations. Thus, when acidulated 
water is electrolyzed, two ions are evolved, namely, oxygen 
and hydrogen, the former at the positive, and the latter at the 
negative, electrode. 

It is absolutely necessary for the electrolyte to be in a fluid 
state, though it does not matter whether the fluid state is pro- 
duced by solution or fusion. 

We know no more of the actual cause of the chemical action 
of electricity than of its nature and origin. According to 
Clausius' theory, matter is composed of minute particles called 
molecules, which, though mechanically indivisible, are chem- 
ically divisible. The constituent parts of the molecules which 
are no further chemically divisible are called atoms. Clausius 
supposes that the molecules are in constant motion; that in 
solid bodies they move around definite positions of equilib- 
rium, while in fluids even apparently tranquil they move from 
one place to another, constantly revolving and pushing against 
one another without being subjected to a return to their original 
positions. In pushing against one another the molecules are 
decomposed into the atoms of which they are composed. 
Those atoms, however, which have become electro-negative 
under the influence of the current, endeavor to reach the anode, 
while those which have become electro-positive move towards 
the cathode. But in doing this they meet atoms of opposite 



MAGNETISM AND ELECTRICITY. 27 

polarity, with which they reunite to a molecule until they are 
again liberated by this molecule pushing against another, when 
they move further towards the anode. Arriving at the elec- 
trodes, they find no more atoms of opposite polarity with 
which they might unite to a molecule ; both atoms, therefore, 
remain free on the electrodes, while the electrolyte between the 
two electrodes suffers no perceptible change. The atoms are, 
therefore, to be considered as ions. However, in order that 
the ions may be attracted by the electrodes, a current of deter- 
mined electro-motive force is required; as otherwise, though 
the electrolyte may conduct the current, the atoms attract one 
another more vigorously than they are attracted by the elec- 
trode, and again form molecules. To this mutual attraction of 
the atoms of opposite polarity is due the resistance of the 
electrolyte to the transmission of the current, and also the for- 
mation of a current of an opposite direction to that of the 
primary current, which is called the counter or polarizing 
current. 

However, since 1887, when Svante Arrhenius established 
his theory of electrolytic dissociation, Clausius's theory has 
been entirely abandoned. Svante shows that the salts when 
in aqueous solution are, according to the degree of dilution of 
the solution and the nature of the salts, more or less extensively 
dissociated into more proximate electrically charged constitu- 
ents. This property of dissociating in this manner in solutions 
belongs, however, only to certain classes of bodies, namely 
acids, bases and soluble salts. Only those bodies which dis- 
sociate in solution are conductors of the electrical current and 
are called electrolytes, and the electrically charged constituents 
into which the bodies split, are called ions. 

The ions are divided into two classes. By the action of the 
electric current upon the electrolytes, one class moves in the 
direction taken by the positive current, hence towards the 
negative electrode, on which it is separated, since according to 
the electrical theory, electricities of an opposite name attract 
and those of a similar name repel each other. Hence the ions 



28 ELECTRO-DEPOSITION OF METALS. 

which travel towards the negative electrode must be positively- 
charged and they are termed kations. The other ions which 
move in the direction of the negative current, hence towards 
the positive electrode, are negatively charged, and are called 
anion s. 

According to Oswald, the most important ions are as follows : 

1. Kations: 

a. Univalent : Hydrogen, potassium, sodium, lithium, 

calcium, rubidium, thallium, silver, ammonium, cop- 
per (in cupro-combinations), mercury (in mercuro- 
combinations), gold, etc. 

b. Bivalent: Calcium, strontium, barium, magnesium, 

iron, etc. 

c. Trivalent : Aluminium, bismuth, antimony, etc. 

d. Quadrivalent : Tin, iridium. 

2. Anions: 

a. Univalent: Hydroxyl (in bases), chlorine, iodine, 

bromine, fluorine, N0 3 C10 3 C10 4 , besides the anions 
of all monobasic acids. 

b. Bivalent : Sulphur, selenium, S0 4 , and the anions of 

the bibasic acids. 

c. Trivalent : The anions of the tribasic acids. 

The ability of forming ions depends not only on the nature 
of the body, but also on the solvent, and this ability is termed 
power of dissociation. Water possesses the greatest power of 
dissociation, and the formation of ions increases with increased 
dilution of the solution. 

The formation of ions may be effected in various ways, but it 
is most frequently the case that in dissolving salts electrically 
neutral molecules split into ions. But since in the solutions of 
the electrolytes, beside existing ions, there are present electric- 
ally neutral substances, the latter may entirely or partly with- 
draw the charge from the existing ions and thereby themselves 
be changed into the ion-state, while the discharged ions become 
either electrically neutral or pass into a condition with a smaller 
electrical charge. Furthermore, a substance may force a fur- 



MAGNETISM AND ELECTRICITY. 20, 

ther charge upon already existing ions, and thereby be changed 
into the ion-state. 

As mentioned above, only bodies capable of dissociation 
conduct the current, and since dissociation increases with dilu- 
tion, the conducting capacity must also increase up to the state 
of solution in which complete dissociation to ions takes place. 

Owing to this movement of the positive ions to the negative 
pole, and of the negative ions to the positive pole, this phe- 
nomenon is termed the traveling of the ions, and the question 
arises whether the velocity with which the ions move is the 
same for all or not. By experiments Hittorfs has shown that 
the ions possess unequal traveling velocity, because the con- 
centration and composition of the electrolytes, which were pre- 
cisely similar before the action of the current on the anode and 
the cathode, showed differences after continued action of the 
current, an increase of the negative ion having taken place on 
the one hand, and a decrease of the positive ion on the other. 

For the better understanding of this more modern theory it 
will be necessary to add a few more brief theoretical observa- 
tions. Like gas, molecules exert upon the walls of the space 
confining them a pressure which is inversely proportional to 
the volume ; solutions of substances also exert a pressure which 
is called osmotic pressure. However, this pressure cannot be 
directly recognized because it is fixed to the volume of the sol- 
vent, the surface of which acts like the rigid walls of the holder 
enclosing the gas. Owing to the surface-tension, i. e., the ten- 
sion of the surface-layers, in consequence of which the latter 
endeavor to become smaller, a pressure is exerted upon the 
interior of the solution which is inversely greater than the pres- 
sure directed against the surface of dissolved bodies. If, how- 
ever, a porous vessel containing solution is placed in another 
vessel holding pure solvent, whereby the surface-tension on the 
walls of the porous vessel is relieved, the pressure of the solu- 
tion, which endeavors to increase the volume, makes itself felt 
by the entrance of the solvent into the solution through the 
porous wall. By the selection of suitable membranes this diffu- 



30 ELECTRO-DEPOSITION OF METALS. 

sion can be debarred so that the augmented volume of the 
solution contains the same quantity of the dissolved body as the 
previously more concentrated solution. If, on the other hand, 
there is a pressure in the solution which endeavors to decrease 
the volume, it is produced by the withdrawal of solvent from 
the porous vessel. 

According to modern views, the formation of the polarizing 
current is explained as follows : Every atom which is separated 
by the electric current on the electrodes possesses a certain 
electrolytic solvent pressure which endeavors to reconstruct 
the separated atom as an ion into the electrolyte. This creates 
an electromotive counter-force opposed to the primary current, 
the latter being thereby weakened. Ihe polarizing current 
follows the same laws as the primary current, and grows with 
the increasing intensity of the latter. 

Now the primary current can pass through the electrolyte 
only when its electromotive force is greater than that of the 
polarizing current. If the decomposition of the electrolyte is 
induced by a weak primary current, the polarizing current may 
possess greater electromotive force, and the primary current 
must be strengthened for the decomposition of the electrolyte. 
The point at which the primary current just overcomes the 
polarizing current and continuous decomposition of the electro- 
lyte is rendered possible is called the decomposition-point, and 
the resulting values for metallic solutions are termed decom- 
position-values. These vary for the several metallic salts, and 
this explains why from a solution containing different metals in 
the form of salts, the separate metals may be separated one 
after the other with a varying current-tension. 

For the purposes of this treatise it would carry us too far to 
enter further into a purely scientific discussion of electro- 
chemistry, and we now turn our attention to the electrolytic 
laws discovered by Faraday. 

First law. The quantity of substance separated within a de- 
termined time by the current is directly proportional to the strength 
of the current. By conducting the current through a volt- 



MAGNETISM AND ELECTRICITY. 



31 



Fig. 6. 




meter (Fig. 6), i. e., a closed decomposing cell provided with 
two platinum electrodes, which are 
in contact with the poles of the 
element, and dip into acidulated 
water, oxygen evolves en the posi- 
tive electrode and hydrogen on the 
negative. The gas mixture (oxy- 
hydrogen gas) is conducted through 
a bent tube inserted air-tight in the 
stopper of the cell, into graduated 
tubes, in such a manner that the 
gas enters the tubes under water. 
The escaping mixture of gas rises in 
the form of bubbles into the upper 
part of the tube, and the volume of 
gas there collected in a determined 
time can be readily read off. 

Now, if a current of determined 
strength has produced a determined 

quantity of oxyhydrogen gas in the voltmeter, a current twice 
as strong will, according to Faraday's law, produce in the same 
time double the volume of gas, from which further results the 
fact that for the decomposition of a determined quantity of any 
body, a constant quantity of current is always required, to 
which the term electrical equivalent might be applied. 

Second law. If the same current acts upon a series of differ- 
ent solutions, the weights of the elements separated at the same 
time in each solution are proportional to their chemical equiva- 
lents. If, for instance, the same current be conducted through 
three decomposing cells, one of which contains water, the 
second a solution of blue vitriol, and the third a solution of 
nitrate of silver, for each gramme of hydrogen developed in the 
first cell, 31.75 grammes of copper will be separated in the 
second cell, and 108 grammes of silver in the third cell, be- 
cause their chemical equivalents are as 1 : 31.75 : 108. 

Third law. In an element, the chemical decomposition — the 



32 ELECTRO-DEPOSITION OF METALS. 

dissolution of zinc — is proportional to the strength of current; or, 
in other words, as many equivalents of zinc are dissolved in the 
element as equivalents of another metal are separated in an in- 
terposed electrolyte. Every electro- plater observes that the zinc 
cylinders of the elements are dissolved ; and it is just this solu- 
tion which maintains the development of the electric current. 
As is well known, zinc is strongly attacked and dissolved by 
dilute sulphuric acid ; therefore a dissolution of zinc takes place 
before the galvanic apparatus is closed. This dissolution of 
zinc, independent of the production of current, is termed local 
action, and to decrease it the zinc is amalgamated by first wash- 
ing it with strong soda to remove grease. Then it is dipped 
into a vessel of water containing y - of sulphuric acid. As 
soon as strong action takes place it is transferred to a suitable 
dish, mercury poured over it, and finally is rubbed till a bright 
silver-like film forms. It is then set up on edge to drain, and 
before use any globules set free are rubbed ofT. If local action 
has thus been prevented, only as much zinc will dissolve, 
according to this law, as is chemically equivalent to the metal 
separated in the decomposing cell. If, however, local action is 
present, the consumption of zinc is increased by the quantity 
corresponding to solution by local action. 

Electro chemical equivalents. — This term is applied to the 
weights of the various electrolytes which are decomposed in 
the unit of time by the electric unit. The electro-chemical 
equivalents are proportional to their chemical equivalents. The 
electro-chemical equivalent of a body is found by multiplying 
its chemical equivalent by the electro-chemical equivalent of 
hydrogen = 0.0001022. 

When an electric current passes through a conductor, the 
latter becomes more or less heated. According to Joule's ex- 
periments, it was found that the development of heat in the con- 
ductor is proportional to its resistance ; and further, that it is 
proportional to the square of the strength of current. 

Hence the development of heat will be the greater the 
smaller the cross-section of the conductor and its conducting 



MAGNETISM AND ELECTRICITY. 33 

capacity are, and the larger the quantity of current which 
passes through it. For practical purposes, the conclusion de- 
rived from this is the necessity of choosing conducting wire of 
good conducting capacity and of sufficiently large diameter to 
prevent the development of heat, which in this case means loss 
of current. 

Consumption of power in electrolysis. — Without a desire fur- 
ther to enter into the details of the electro-chemical theory, it 
may for the sake of completeness be mentioned that the force 
required for the decomposition of an electrolytic solution is at least 
equal to that which, when converted into heat, corresponds to the 
heat developed by the separated bodies in their reunion into their 
original combination. 

Electric units. — The electro-motive force required for the de- 
composition being frequently given, as well as the intensity 
which the current must possess in order properly to coat a de- 
termined surface of article with the electrolytically separated 
metal, the electric units serving for electric measures will be 
briefly given : 

To measure the physical phenomena of the current it is 
necessary to refer to mass, length, and duration of time, and 
the units adopted by the International Congress of 1881 are as 
follows : — 

1. Unit of length, 1 centimetre. 

2. Unit of time, I second. 

3. Unit of mass, the mass of one gramme. 

The term fundamental or C. G. S. ^ centimetre-gramme-sec- 
ond) units has been applied to this system. 

Force or power (F) — Dyne. — Force which acting upon 1 
gramme for a second generates a velocity of 1 centimetre per 
second. 

Work — Erg. — Amount of work done by 1 dyne working: 
through 1 centimetre of distance. 

Quantity. — The quantity conveyed by unit current in 1 
second. 

Potential or electro-motive force. — The difference of the electric 

3 



34 ELECTRO-DEPOSITION OF METALS. 

condition between two conductors or two points of a conductor, 
when the transference of electricity from one to the other is 
proceeding at the rate of I erg of work per unit of electricity 
transferred. 

Resistance. — A resistance such that with unit of difference of 
potential between the ends of conductor, I unit of current is 
conveyed along it. 

Of the so-called practical units, which were retained by the 
Congresses and Conferences of 1 88 1 and 1884, there are five: 
the ohm, volt, ampere, farad, and coulomb. 

The ohm is the practical unit of resistance. It is equal to 
the resistance of a column of mercury 1 metre long and 1 
square millimetre in cross-sectional area at o° C, and approxi- 
mately equal to the resistance of 48.5 metres of pure copper 
wire, 1 millimetre in diameter, at 0° C. The ohm is equal to 
109 C. G. S. units. 

The ampere is the practical unit of the current-strength (in- 
tensity) ; it is equal to T V of the theoretical C. G. S. unit. For 
practical purposes the quantity of silver precipitated in one 
second is taken as the representative value of an ampere, 
0.0011188 gramme of silver corresponding, according to Kohl 
rausch, to one ampere. 

The volt is the practical unit of the electro motive force, and 
is equal to io 8 C. G. S. units. It is approximately equal to the 
electro-motive force of a single Daniell's cell. 

The farad is the practical unit of capacity equal to 10 9 C. G. 
S. units; the coulomb is the unit of quantity, i. e., the volume 
of current equal to that of 1 ampere passing through a circuit 
for one second of time. 

A current of 1 ampere at the pressure of 1 volt is termed a 
watt ; it is a most useful unit for comparing different currents, 
and is really the product of volume into pressure. 

The English horse-power (H. P.) is taken at 550 foot-pounds 
per second, and is thus equivalent to raising 550 pounds 
through one foot, or one pound through 550 feet, in a second. 
(The French H. P. is 542.48 foot-pounds per second.) 



III. 

SOURCES OF CURRENT. 



CHAPTER III. 



f GALVANIC ELEMENTS — THERMO-PILES — MAGNETO- AND 
DYNAMO-ELECTRIC MACHINES. 

THE sources of current used for electro-deposition ©f metals 
are the galvanic elements, thermo-piles, magneto-electric ma- 
chines, and dynamo-electric machines. 

A. Galvanic Elements. 

It is not proposed to enter into a detailed description of all 
the forms of galvanic elements, because the number of such 
constructions is very large, while the number of those which 
have been successfully and permanently introduced for prac- 
tical work is comparatively small. 

The original form of the galvanic elements, the voltaic pile, 
consisting of zinc and copper plates separated from one another 
by moist pieces of cloth, has been already mentioned on p. 2, 
as well as its disadvantages, which led to the construction of the 
so-called trough battery. The separate elements of this battery 
are square plates of copper and zinc, soldered together and 
parallel, fixed into water-tight grooves in the sides of a wooden 
trough so as to constitute water-tight partitions, which are filled 
with acidulated water. The layer of water serves here as a 
substitute for the moist pieces of cloth in the voltaic pile. 

In other constructions the fluid is in different vessels, each 

(35) 



36 ELECTRO-DEPOSITION OP METALS. 

vessel containing a zinc and a copper plate which do not touch 
one another in the same vessel, the copper plate of the one 
vessel being connected with the zinc plate of the next, and 
so on. 

In all elements with one fluid as an excitant, the current is 
quite strong at first, but quickly decreases for the following 
reasons : First, during the interruption of the current, a change 
takes place in the fluid by the local action in the element, and 
then with a closed circuit the zinc with the impurities it con- 
tains forms small voltaic piles, the element consequently also 
performing a certain chemical work during the interruption of 
the current. As mentioned on p. 32, the local action can be 
reduced to a minimum by amalgamating the zinc. Such 
amalgamation is also a protection against the above-mentioned 
chemical work of the element, the bubbles of hydrogen adher- 
ing so firmly to the amalgamated homogeneous surface as to 
form a layer of gas around the zinc surface, which prevents its 
contact with the fluid. 

Amalgamation may be effected in various ways. The zinc is 
either scoured with coarse sand moistened with dilute sulphuric 
or hydrochloric acid, or pickled in a vessel containing either of 
the dilute acids. The mercury may be either mixed with 
moist sand and a few drops of dilute sulphuric acid, and the 
zinc be amalgamated by applying the mixture by means of a 
wisp of straw or a piece of cloth ; or the mercury may be ap- 
plied by itself by means of a steel wire brush, the brush being 
dipped in the mercury, and what adheres is quickly distributed 
upon the zinc by brushing until the entire surface acquires a 
mirror-like appearance. The most convenient mode of amal- 
gamation is to dip the zinc in a suitable solution of mercury 
salt and rub with a woolen rag. A suitable solution is pre- 
pared by dissolving 10 parts by weight of mercurous nitrate in 
100 parts of warm water, to which pure nitric acid is added 
until the milky turbidity disappears. Another solution, which 
is also highly recommended, is obtained by dissolving 10 parts 
by weight of mercuric chloride (corrosive sublimate) in 12 



SOURCES OF CURRENT. 37 

parts of hydrochloric acid and 100 of water, or by dissolving 
IO parts by weight of potassium mercuric cyanide and 2 parts 
potassium cyanide in 100 parts of water. In order to preserve 
as much as possible the coating of mercury upon the zinc, sul- 
phuric acid saturated with neutral mercuric sulphate is used 
for the elements. For this purpose frequently shake the con^ 
centrated sulphuric acid (before diluting with water) with the 
mercury salt. As much mercuric sulphate or mercuric chlo- 
ride as will lie upon the point of a knife may also be added in 
the elements to the zinc. 

Bouant recommends instead of the addition of mercuric sul- 
phate, to compound the dilute sulphuric acid with 2 per cent, 
of a solution obtained as follows: Boil a solution of 3^ ozs. of 
nitrate of mercury in 1 quart of water, with an excess of a mix- 
ture of equal parts of mercuric sulphate and mercuric chloride, 
and, after cooling, filter and use the clear solution. 

The third reason for the decrease of the current-strength in 
elements with one fluid is polarization. By polarization is un- 
derstood the appearance in the element of a second current 
which, being opposite to that produced by the element, weak- 
ens the action of the latter. The cause of galvanic polarization 
is found in the fact that the negative pole-plate becomes coated 
with a layer of hydrogen, from which, in consequence of the 
high electrolytic solution-pressure, the separated hydrogen- 
atoms endeavor to return to the ion-condition. 

Polarization can only be entirely avoided in elements the 
negative pole-plate of which dips into a fluid which oxidizes the 
hydrogen to water, as is the case in the so-called coiistant ele- 
ments with two fluids, as will be seen later on. 

Proceeding from the conviction that rough surfaces allow the 
bubbles of hydrogen to pass off much more freely than smooth 
surfaces, Smee constructed the element named after him. It 
consists of a zinc plate and a platinized silver plate dipping into 
dilute acid. It may be formed of two zinc plates mounted with 
the platinized silver between them in a wooden frame, which 
being a very feeble conductor may carry away a minute fraction 



38 ELECTRO-DEPOSITION OF METALS. 

of the current, but serves to hold the metals in position, so that 
quite a thin sheet of silver may be employed without fear of its 
bending out of shape and making a short circuit. The platiniz- 
ing is effected by suspending the silver plates in a vessel filled 
with acidulated water, adding some chloride of platinum, and 
placing the vessel in a porous clay cell filled with acidulated 
water and containing a piece of zinc, the latter being connected 
with the silver plates by copper wire. The platinum coating 
obtained in this manner is a black powder which roughens the 
surfaces, in consequence of which the bubbles of hydrogen be- 
come readily detached and the polarization is less than with 
silver plates not platinized. The use of electrolytically pre- 
pared copper plates, which are first strongly silvered and then 
platinized, is still more advantageous on account of their 
greater roughness. To increase the constancy of the element, 
it is advisable to add some chloride of platinum to the dilute 
acid of the element. 

The Smee element is still frequently used in England and in 
the United States, especially in processes for which at first a 
higher current-strength is required, whilst later on a less inten- 
sity suffices, or is even necessary, as, for instance, in silvering. 
The electro-motive force is about 0.48 volt. 

As previously mentioned, polarization can be entirely 
avoided only by allowing the electro-negative pole-plate to dip 
in a fluid which, by combustion, reduces the hydrogen evolved 
to water, or, in other words, which immediately oxidizes the 
hydrogen to water. From this conviction originated the so- 
called constant elements with two fluids, the first of these 
elements being, in 1829, constructed by Becquerel, which, 
in 1836, was succeeded by the far more effective one of 
Daniell. 

As most generally used, Daniell's element (Fig. 7) consists 
of a glass vessel, a copper cylinder, a porous clay cell, and a 
rod of zinc suspended in the latter. The glass vessel is filled 
with concentrated solution and a small piece of blue vitriol, 
and the porous clay cell with dilute sulphuric acid. The 



SOURCES OF CURRENT. 



39 



Fig. 7. 




oxygen evolved on the electro-positive zinc oxidizes the latter, 
sulphate of zinc being formed, while the hydrogen separating 
on the electro-negative copper reduces from the blue vitriol 
solution a quantity of copper equivalent to it, which separates 
upon the electro-negative plate. However, 
after a comparatively short time of work- 
ing, the dilute sulphuric acid is consumed 
for the formation of sulphate of zinc, the 
electro-motive force becoming very weak. 
The necessity of frequently renewing the 
dilute sulphuric acid is an inconvenience 
which the Daniell element shows more than 
any other. Furthermore, by the action 
of osmose, blue vitriol solution gets into 
the porous cell, where it is decomposed by 
coming in contact with the zinc, the copper being separated 
upon the latter, whereby the effect is destroyed or at least very 
much weakened. The electro-motive force of the Daniell 
element is about 1 volt. 

The Meidinger element may be considered a modified Daniell 
element. Like the Callaud element, it has no porous division, 
the mixture of the two fluids being prevented by their different 
specific gravities. The shape of the Meidinger element, as 
most generally used, is shown in Fig. 8. 

Upon the botton of a glass vessel, A, provided at b with a 
shoulder, stands a small glass cylinder, K, which contains the 
electro negative copper cylinder D; from the latter a conduct- 
ing wire leads to the exterior. Upon the shoulder, at b, rests 
the zinc cylinder Z, which is also provided with a conducting 
wire leading to the exterior. The balloon C closes the vessel 
by being placed upon it. The balloon is filled with pieces of 
blue vitriol and Epsom salt solution. The entire element is also 
filled with Epsom salt solution ( 1 part Epsom salt to 5 water). 
In the balloon C concentrated solution of blue vitriol is formed 
which flows into the glass cylinder K. If the circuit is not 
closed, the concentrated copper solution remains quietly 



40 



ELECTRO-DEPOSITION OF METALS. 



Fig. 8. 




standing in K, its greater specific gravity preventing it from 
rising higher and reaching the zinc. If, however, the cir- 
cuit be closed, zinc is dissolved, while 
metallic copper is separated from the 
blue vitriol solution, and concentrated 
solution flows from the balloon C to the 
same extent as the blue vitriol solution 
in D becomes dilute by the separation of 
copper. Hence the action of the element 
remains constant for quite a long time, 
and of all the modified forms of Daniell's 
element consumes the least blue vitriol 
for a determined quantity of current. 
However, in consequence of its great in- 
ternal resistance (9.90 ohms) its current- 
strength is small. The electro-motive 
force of the Meidinger element is 0.95 volt. 
Grove, in 1839, substituted platinum for copper. The plati- 
num dips in concentrated nitric acid, while the zinc cylinder 
stands in dilute sulphuric acid. The hydrogen liberated on 
the platinum is oxidized to water by the nitric acid, hypo- 
nitrous acid escaping in the form of gas. The electro-motive 
force of the Grove element is at first double that of the Daniell 
element, but it soon abates on account of the dilution of the 
nitric acid by water. To prevent this weakening, concentrated 
sulphuric acid, which absorbs the water formed by the oxida- 
tion of the hydrogen, may be added to the nitric acid. Though 
the resistance of the Grove element is small (0.7 to 0.75 ohm), 
and its electro-motive force 1.70 to 1.90 volts, according to the 
concentration of the solutions, it is but seldom used on account 
of its costliness. 

Bunsen, in 1841, replaced the expensive platinum by prisms 
cut from gas-carbon, which is still less electro-negative than 
platinum, and very hard and solid, so that it perfectly resists 
the action of the nitric acid. In place of the gas-carbon an 
artificial carbon may be prepared by kneading a mixture of 



SOURCES OF CURRENT. 



41 



pulverized coal and coke with sugar solution or syrup, bringing 
the mass under pressure into suitable iron moulds and igniting 
it with the exclusion of air. After cooling, the carbon is again 
saturated with sugar solution (others use tar, or a mixture of 
tar and glycerine) and again ignited with the exclusion of air, 
these operations being, if necessary, repeated once more, es- 
pecially when great demands are made on the electro motive 
force and solidity of the artificial carbons. 

Figs. 9, 10, and 11 show the three forms of Bunsen's ele- 
ments most generally used. 

Fig. 9, which is the most convenient and practical form, con- 
sists of an outer vessel of glass or earthenware. In this is 



Fig. 9. 



Fig. 10. 



Fig. 11. 






placed a cylinder of zinc in which stands a porous clay cell, 
and in the latter the prism of gas-carbon. This substance is 
the graphite of the gas retorts. It is not coke. It is easily 
procurable in lump at a small price, but costs much more when 
cut into plates, as, when the material is good, it is exceedingly 
difficult to work. It is generally cut with a thin strip of iron 
and watered silver-sand. Blocks of Bunsen cells cost less be- 
cause they are more easily produced. Rods for Bunsen cells 
should be a few inches longer than the pots to protect the top 
contact from the acid. A good carbon is of a clear gray ap- 
pearance, has a finely granulated surface, and is very hard. A 



42 



ELECTRO DEPOSITION OF METALS. 



band of copper is soldered or secured by means of a binding- 
screw to the zinc cylinder, while the prism of gas-carbon carries 
the binding-screw (armature), as seen in Fig. 9, in the upper 
part of which a copper sheet or wire is fixed for the transmis- 
sion of the current. The other vessel is filled with dilute sul- 
phuric acid (1 part by weight of sulphuric acid of 66° Be. — 
free from arsenic — and 15 parts by weight of water), and the 
porous cell with concentrated nitric acid of at least 36 Be., or 
still better 40 Be., care being had that both fluids have the 
same level. 

In Fig. 10 the cylinder of artificial carbon is in the glass ves- 

FlG. 12. 




sel, while the zinc, which, in order to increase its surface, has a 
star-like cross-section, is placed in the porous clay cell. In 
this case the outer vessel is filled with concentrated nitric acid, 
and the clay cell with dilute sulphuric acid. 

The form of the Bunsen element shown in Fig. 9 is more 
advantageous, because its effective zinc surface can be kept 
larger. Fig. 1 1 shows a plate element such as is chiefly used 
for bichromate batteries. 

Fig. 12 shows an improved Bunsen cell of great power for 
nickel and electro-plating, electro-motors, etc. It has an elec- 



SOURCES OF CURRENT. 43 

tro-motive force of 1.8 volts. When the absence of power pre- 
vents the use of a dynamo, a battery of these elements is very suit- 
able for nickel-plating. It is an easy battery to set up and keep 
in working order. The batteries are set up by well amalgamat- 
ing, inside and outside, the zinc, and placing it in the jar. In- 
side the zinc, place the porous cup, and within the porous cup 
the carbon, and then pour nitric acid in the porous cup. In 
the outer jar pour a mixture of I part sulphuric acid to 12 of 
water (previously mixed and allowed to cool).* This acid mix- 
ture should cover the zinc or be on a level with the liquid in 
the porous cup. When the liquid in the outer jar becomes 
milky, withdraw it with a syringe or siphon, and refill, adding 
occasionally small quantities of nitric acid to the porous cup, 
and keeping the zinc thoroughly amalgamated by one of the 
methods given on page 36. A very good plan of amalgamat- 
ing zinc is as follows : Dip in lye to remove grease, rinse, 
next dip in the dilute acid in the glass jar, and then brush 
over with about 2 ozs. of mercury contained in a little flannel 
bag. 

Electropoion may be substituted for the nitric acid in the por- 
ous cup. This battery liquid consists of t lb. of bichromate 
of potash dissolved in 10 lbs. of water, to which 2 x / 2 lbs. of 
commercial sulphuric acid have been gradually added. 

The Bunsen elements are much used for electro-deposition, 
since they possess a high electro-motive force (1.88 volts) and, 
on account of slight resistance (0.25 ohm), develop consider- 
able current-strength. Like the Grove element, they have the 
inconvenience of evolving vapors of hyponitrous acid, which 
are not only injurious to health, but also attack the metallic 
articles in the workshop. Wherever possible they should be 
placed in a box at such a height that they may be readily 
manipulated. This box should have means of ventilation in 
such a way that the air coming in at the lower part will escape 
at the top through a flue, and carry away with it the acid 

*The sulphuric acid should be poured into the water; not che water into the acid. 



44 EEECTRO-DEPOSITION OF METALS. 

fumes disengaged. It is still better to keep the elements in a 
room separate from that where the baths and metals are located. 
Furthermore, as the nitric acid becomes diluted by the oxida- 
tion of the hydrogen, and the sulphuric acid is consumed in 
the formation of sulphate of zinc, the acids have to be fre- 
quently renewed. 

To avoid the acid vapors, as well as to render the elements 
more constant, A. Dupre has proposed the use of a 30 per cent, 
solution of bisulphate of potash in water in place of the dilute 
sulphuric acid, and a mixture of water 600 parts, concentrated 
sulphuric acid 400, sodium nitrate 500, and bichromate of 
potash 60, in place of the nitric acid. 

The following method can be recommended : The outer 
vessel which contains the zinc cylinder is filled with a mode- 
rately concentrated (about 30 per cent.) solution of bisulphate 
of potash or soda, and the clay cell with solution of chromic 
acid — 1 part chromic acid to 5 parts water. As soon as the 
electro-motive force of the element abates, it is strengthened by 
the addition of a few spoonfuls of pulverized chromic acid to 
the chromic acid solution. It is better to use the chromic acid 
in the form of powder, which is especially prepared for this 
purpose, than a chromic acid solution produced by mixing 
solution of bichromate of potash with sulphuric acid, a disturb- 
ing effect being exerted by the tendency of such a solution to 
form crystals. 

The chromic acid solution loses effect in a comparatively 
short time, the electro-motive force decreasing in a few hours, 
and chromic acid must be added, or the element refilled. 

Another soluble chromium combination which depolarizes 
with rapidity and maintains the constancy of the elements for a 
much longer time, is obtained by treating pulverized chrome- 
ironstone with concentrated sulphuric acid and carefully dilut- 
ing with water. With a single filling of this solution the 
battery may be kept working for six days from morning to 
evening without refilling being required. During the nights 
the battery remains filled but inactive. The electro motive 



SOURCES OF CURRENT. 45 

force of an element filled with this solution is 1.8 volts. On 
account of its lasting quality and great constancy, and conse- 
quent cheapness, this filling would appear to be the most 
suitable. 

In using nitric acid it is also advantageous to pour a 0.39 to 
0.78 inch thick layer of oil upon the acid, to decrease the 
vapors. 

The binding-screws which effect the metallic contacts must 
of course be frequently inspected and cleaned, which is best 
done by means of a file or emery paper. It is advisable to 
place a piece of platinum sheet between the binding surface of 
the carbon armature and the carbon in order to prevent the 
acid rising through the capillarity of the carbon from acting 
directly upon the armature (generally brass or copper). To 
prevent the acid from rising, the upper portions of the carbons 
may be impregnated with paraffine. For this purpose the car- 
bons are placed ^ to I inch deep in melted paraffine and 
allowed to remain 10 minutes. On the sides where the arma- 
ture comes in contact with the carbon, an excess of paraffine 
is removed by scraping with a knife-blade or rasp. 

Manipulation of Bunsen elements. — Before using the elements 
the zinc cylinders should be very carefully amalgamated accord- 
ing to one of the methods given on p. 36. The nitric acid need 
not be pure, the crude commercial acid sufficing, but it should 
be as concentrated as possible and show at least 36 Be. For 
the prisms it is best to take carbon produced in gas houses 
using coal without the addition of lignite or brown coal, the 
electro-motive force of the latter being less. If artificial carbon 
is employed, it should be examined as to its suitability, the non- 
success of the plating process being frequently attributed to the 
composition of the bath, when in fact it is due to the defective 
carbons of the elements. In order to avoid an unnecessary 
consumption of zinc and acid, the elements are taken apart 
when not in use, for instance, over night. Detach the brass 
armature of the carbon prism and lay it in water to which som e 
chalk has been added. Lift the carbon from the clay cylinder 



46 ELECTRO-DEPOSITION OF METALS. 

and place it in a porcelain dish or earthenware pot; empty the 
nitric acid of the clay cell into a bottle provided with a glass 
stopper; place the clay cell in a vessel of water, and finally 
take the zinc cylinder from the dilute sulphuric acid and place 
it upon two sticks of wood laid across the glass vessel to drain 
off. In putting the elements together the reverse order is fol- 
lowed, the zinc being first placed in the glass vessel and then 
the carbon in the porous clay cell. The latter is then filled 
about three-quarters full with used nitric acid, and fresh acid is 
added until the fluid in the clay vessel stands at a level with 
that in the outer vessel. The cleansed brass armature is then 
screwed upon the carbon prism. Finally, add to the dilute 
sulphuric acid in the outer vessel a small quantity of concen- 
trated sulphuric acid saturated with mercury salt. 

It is advisable to have at least a duplicate set of porous clay 
cells, and in putting the elements together to use only cells 
which have been thoroughly soaked in water. The reason for 
this is as follows : The nitric acid fills the pores of the cell, and, 
finally reaching the zinc of the outer vessel, causes strong local 
action and a correspondingly rapid destruction of the zinc. It 
is, therefore, best to change the clay cells every day, allowing 
those which have been in use to lie in water the next day with 
frequent renewal of the water. For the same reason the nitric 
acid in the clay cell should not be at a higher level than the 
sulphuric acid in the outer vessel. 

When the Bunsen elements are in steady use from morning 
till night, the acids will have to be entirely renewed every third 
or fourth day. The solution of sulphate of zinc in the outer 
vessel being of no value is thrown away, while the acid of the 
clay cells may be mixed with an equal volume of concentrated 
sulphuric acid, and this mixture can be used as a preliminary 
pickle for brass and other copper alloys. 

Foote's pinnacle gravity battery. Gravity batteries are es- 
pecially suited for continuous work at a low rate, the operating 
cost being as low as, if not lower than, any other type of bat- 
tery. Four of these cells in series will charge a small storage 



SOURCES OF CURRENT. 



47 



battery. The type of gravity shown in Fig. 13 is one of the 
best in the market. 

The battery is set up by placing the copper cross and zinc 
in position. Pour clean water into 
the jar until within two inches of 
the top, then drop in blue vitriol 
(sulphate of copper) in small 
lumps. The battery may be made 
immediately available by adding 4 
ozs. of pulverized sulphate of zinc. 
When the hydrometer reads less 
than 1 5 Be., there is too much. 

Oppermanri s element is in the 
main a Bunsen element quite free 
from odor, but is distinguished from 
the latter by a hollow porcelain 
body which is placed upon the clay 
cell and filled with potassium per- 
manganate solution whereby the es- 
caping vapors are mostly rendered innocuous. Besides, the ele- 
ment when at rest consumes no materials. To avoid the incon- 
venience of emptying the elements, the battery jars are pro- 
vided, close above the bottoms, with two tubulures opposite to 
one another. This arrangement allows of all the jars of a 
battery being connected by means of glass tubes and rubber 
hose as shown in Fig. 14. The first jar of the battery is con- 
nected by means of a rubber hose of suitable length with a 
large tubulated supply-jar, while one of the tubulures of the 
last jar is provided with a massive rubber stopper. The supply- 
jar contains the exciting fluid for the outer cells. 

The clay cell of the Oppermann element is closed by a 
hollow porcelain lid. The latter contains a fluid capable of 
absorbing or decomposing the vapors evolved by the decom- 
position of the depolarizing fluid containing nitric acid. In the 
centre of the porcelain lid is a square hole in which the carbon 
prism is secured. The fluid in the lid consists of a solution of 




4 8 



ELECTRO-DEPOSITION OF METALS. 



potassium permanganate acidulated with a small quantity of 
sulphuric acid. The solution is prepared as follows : Dissolve 
I part by weight of pure potassium permanganate in 20 parts 
by weight of distilled water, and add to the solution about 1 
part by weight of dilute sulphuric acid. The vapors of hypo- 
nitrous acid are absorbed with avidity by this solution, and 
oxidized partly to nitrous acid and partly to nitric acid. Both 
of these acids combine with the potassium or the manganous 
oxide, and the potassium permanganate solution, which 

Fig. 14. 




exhibits at first a deep violet color, is finally completely de- 
colorized. When this is the case, which will be in about 3 or 
4 hours, the solution has to be renewed. This is done in the 
simplest manner by introducing about 5 ccm. of the solution 
into the lid by means of a pipette, whereby the solution con- 
sumed is forced from the lid, passes into the clay cell and 
enriches the depolarizing fluid by the addition of fresh nitric or 
nitrous acid. 



SOURCES OF CURRENT. 49 

The arrangement of the elements and their combination to a 
battery is effected as follows : The battery jars are placed as 
indicated in the illustration and connected with one another by 
means of rubber stoppers, glass tubes bent at a right angle and 
short pieces of rubber hose. It is advisable first to dip the 
rubber stoppers in water, then to press them firmly into the 
tubulures, and finally to insert the glass tubes also previously 
moistened with water. For the sake of security the rubber 
stoppers are fastened to the tubulus with cord or wire. One 
tubulus each of the two end jars, however, remains free. The 
free tubulus of the last jar is tightly closed with a massive 
rubber stopper, while that of the first jar is provided with a per- 
forated stopper and a glass tube, and is connected with the 
supply-jar by means of a rubber hose of suitable length. 

In the battery-jars thus connected the zinc cylinders are first 
placed, and next in the latter the clay cells, and finally in the 
clay cells the carbon prisms. The clay cells are then filled 
with nitric acid of 40 Be. The porcelain lids are next placed 
upon the carbon prisms and the brass binding-screws secured 
to the prisms. The size of the porcelain lids must be such that 
they reach into the clay cells and are about even with the upper 
edge of the latter. The holes on the upper side of the porce- 
lain lids remain open. For filling the lids with potassium per- 
manganate solution a pipette is used. At 5 ccm. the pipette is 
provided with a mark, and it is filled up to that point by dip- 
ping it in the fluid or by suction. The upper opening is then 
closed with the index finger of the right hand and the point of 
the pipette introduced into the hole of the lid. By now remov- 
ing the finger the contents of the pipette run into the lid. 

For filling the outer cells it is best to use a concentrated solu- 
tion of common salt, which is prepared by dissolving 35 parts 
by weight of common salt in 100 parts by weight of water. 
Should the solution be very turbid, it has to be filtered. This 
is also necessary in case the solution, while in use, deposits a 
muddy sediment. In place of common salt solution, a concen- 
trated sal ammoniac solution may be used. It is prepared by 
4 



50 ELECTRO-DEPOSITION OF METALS. 

dissolving 25 parts by weight of sal ammoniac in 75 parts 
by weight of water. Dilute sulphuric acid ( 1 part by weight of 
pure sulphuric acid in 30 parts by weight of water), with an 
addition of a small quantity of neutral sulphate of mercury, is 
also suitable as an exciting fluid. Common salt solution, how- 
ever, deserves preference; and its action can be strengthened 
by the addition of a very small quantity of dilute sulphuric acid. 
The exciting fluid is brought into the supply-jar. The ordinary 
element is 7.87 inches in height and, when this size is used, 
the supply-jar must have a capacity of at least as many quarts 
as there are elements in the battery. To fill the jars the 
supply-jar is placed at a higher level and the cock opened. 
The solution then runs into all the battery-jars connected with 
one another. After connecting the copper band of the zinc 
cylinder with the binding-screw of the carbon of the next ele- 
ment, the battery is ready for use. To connect the end poles 
of the battery with the respective apparatus, quite stout copper 
wire thoroughly insulated should be used. The wire should 
be 0.079 inch in diameter, and be as short as possible. 

When work with the battery is to be interrupted, the supply- 
jar is placed at a lower level and the cock opened. The ex- 
citing fluid then escapes from the outer cells of the elements, 
and the development of current ceases. While the battery is 
not in use, a small portion of the depolarizing fluid oozes 
through the clay cells and collects upon the bottom of the bat- 
tery-jars. This fluid must be removed before the battery is 
again put in operation. For this purpose the glass tubes bent 
at a right angle inserted in the tubulures of the jars are turned 
so that one leg points upwards. The rubber hoses are then 
withdrawn, the bent glass tubes turned downward and the jars 
emptied by tilting them. For filling the clay cells with fresh 
nitric acid, a glass funnel with glass cock and long discharge 
tube is used, whereby it is, however, necessary to slightly lift 
the porcelain lid in order to reach the interior of the clay cell. 
The clay cells require emptying entirely only when the battery 
is not to be used for some time or when it is to be cleaned, 



SOURCES OF CURRENT. 5 I 

which has to be done once in a while. When the exciting 
fluid in the outer cells has become ineffective, it has to be 
replaced by a fresh supply. How often the battery has to be 
cleansed and how often the exciting fluid has to be renewed, 
depends of course on the length of time the battery is in use. 

The efficacy of the battery can be still further increased by 
keeping the exciting fluid in the exterior cells in constant cir- 
culation, which is effected as follows : Each of the two end 
cells of the battery is connected with a supply-jar of suitable 
capacity and the full jar of the two supply-jars is placed at a 
higher, and the empty jar at a lower, level. By means of a 
screw-clip the discharge and influx of the fluid are so regulated 
that the latter always stands at the same, level. When the 
upper jar is empty, the position of the jars is reversed. By 
now placing the two supply-jars in a tub containing ice and 
thus constantly cooling the circulating exciting fluid, the heat- 
ing of the elements which otherwise constantly takes place is 
avoided, and the battery can be kept working for a longer time 
without interruption. 

The ordinary Oppermann element, which is 7.87 inches high, 
has an electro-motive force of 1.85 to nearly 1.9 volts. The 
current strength measured on the open element by means of 
the spiral ammeter is 15 to 20 amperes. The quantity of oxy- 
hydrogen gas evolved, measured by the voltmeter, amounts to 
about 20 ccm. per minute. 

The Leclanche element (zinc and carbon in sal ammoniac 
solution with manganese peroxide as a depolarizer; need not 
be further described, it not being adapted for regular use in 
electro-plating. It is in very general use for electric bells, its 
great recommendation being that, when once charged, it retains 
its power without attention for several years. 

Lallande and Chaperon have introduced a copper oxide 
element, shown in Fig. 15, which possesses several advan- 
tages. It consists of the outer vessel G, of cast-iron or cop- 
per, which forms the negative pole surface, and to which the 
wire leading to the anodes is attached, and a strip of zinc, Z, 



*2 



ELECTRO-DEPOSITION OF METALS. 



coiled in the form of a spiral, which is suspended from an 
ebonite cover carrying a terminal connected with the zinc. The 
hermetical closing of the vessel G by the ebonite cover is 
effected by means of three screws and an intermediate rubber 
plate. Upon the bottom of the vessel G is placed a 3 to 4 inch 
deep layer of copper oxide, 0, and the vessel is filled with a 
solution of 50 parts of caustic potash in 100 of water. When 
the element is closed, decomposition of water takes place, the 
oxygen which appears on the zinc forming with the latter zinc 
oxide, which readily dissolves in the caustic potash solution, 



Fig. 15 




while the hydrogen is oxidized with the simultaneous reduction 
of copper oxide to copper. When the element is open, i. e. } 
the circuit not closed, neither the zinc nor the copper oxide is 
attacked, and hence no local action nor any consumption of 
material takes place. The electro-motive force of this element 
is 0.98 volt, and its internal resistance very low. It is remark- 
ably constant, and is well adapted for electro-plating purposes 
by using two of them for one Bunsen element. The following 
rules have to be observed in its use. It is absolutely necessary 
that the ebonite cover should hermetically close the vessel G, as 



SOURCES OF CURRENT. 53 

otherwise the caustic potash solution would absorb carbonic 
acid from the air, whereby carbonate of potash would be 
formed, which would weaken the exciting action of the solu- 
tion. Further, the vessels G which form one of the poles must 
be insulated one from the other as well as from the ground, as 
otherwise a loss of current or defective working would be the 
consequence. 

The regeneration of the cuprous oxide or metallic copper 
formed by reduction from the cupric oxide to cuprous oxide, 
requires it to be subjected to calcination in a special furnace. 
The expense connected with this operation is, however, about 
the same as that of procuring a fresh supply of cupric oxide. 
Lallande himself, as well as Edison, endeavored to bring the 
pulverulent cupric oxide into compact plates, but the regenera- 
tion of these plates was still more troublesome. By treatment 
with various chemical agents, Dr. Bottcher, of Leipsic, has suc- 
ceeded in producing porous plates of cupric oxide which, after 
subsequent reduction by absorption of oxygen from the air, 
can be readily re-oxidized to cupric oxide, but as far as we 
know, elements with these plates have not yet been introduced 
into commerce. 

Umbreit & Matthes bring into commerce an element known 
as cupron element, which is an improved Lallande element, and 
in which the cupric oxide is also brought into the form of 
plates. A square glass vessel or vat with a ground edge 
and closed with a hard-rubber lid contains two zinc plates, and 
between the latter the porous cupric oxide plate. The glass 
vessel is filled with 20 per cent, caustic soda lye, and the cur- 
rent is delivered through two clamps on the outside of the lid. 
According to Umbreit and Matthes' statements the reduced 
positive pole plates are regenerated, that is, re-oxidized to 
cuprous oxide by rinsing in water and allowing them to remain 
in a warm place for 20 to 24 hours, so that it is only necessary 
to replace the soda lye saturated with zinc oxide. The 
electro-motive force of the element is 0.8 volt; the normal 
current-strength, according to the size of the elements 1, 2, 4 



54 ELECTRO-DEPOSITION OF METALS. 

and 8 amperes. Like the Lallande element, this element 
works without odor. An addition of sodium hyposulphite to 
the soda lye is claimed to produce uniform wear and greater 
durability of the zinc plates. 

The elements of Marie, Davy, Niaudet, Duchemin, Sturgeon, 
Trouville, and others, being of little practical value, may be 
passed over. 

Dun s potash element. On account of its great electro- 
motive force (1.6 volts) and slight internal resistance, this ele- 
ment would be well adapted for electro-plating purposes, if 
depolarization were effected more rapidly than is actually the 
case. Its construction is as follows : In a glass vessel stands a 
hollow coke cylinder fitted with a bottom, and in the centre of 
the coke cylinder a clay cell. The space between the clay cell 
and the interior wall of the coke cylinder is filled five-sixths 
full with pieces of coke. In the clay cell stands an amalga- 
mated strip of zinc or zinc cylinder to which the conducting 
wires are soldered, the place of soldering, as well as the wire as 
far as it comes in contact with the fluid, being covered with 
gutta-percha. The edge of the coke cylinder is coated with 
paraffine and carries the pole binding-screw. The filling of 
the element is effected by laying potassium permanganate in 
crystals upon the layer of carbon between the clay and coke 
cylinders, and pouring a solution of r part of pure caustic 
potash in 2 of water into the clay cell, the pouring being con- 
tinued until the fluid runs over the clay cell upon the potassium 
permanganate and the layer of coke, and finally fills the outer 
vessel up to about the breadth of two fingers from the edge. 
The action of the element is as follows : When the element 
is closed decomposition of water takes place, the oxygen com- 
bining with the zinc to form zinc oxide, which is dissolved by 
the potash lye, while the hydrogen is oxidized on the positive 
pole by the potassium permanganate. The latter, to be sure, 
contains much oxygen, and acts very energetically, but as it 
diffuses very slowly, depolarization, i. e., the removal of the 
hydrogen, is not so rapidly effected as, for instance, in the 



SOURCES OF CURRENT. 



55 



Fig. i 6. 



Bunsen element, where the nitric acid rapidly diffuses. Hence 
with a slight external resistance, for instance, baths where the 
element has to furnish large quantities of current, the electro- 
motive force sinks very rapidly and with it the current strength, 
and, therefore, the element is only suitable for electro-plating 
purposes when a current is only required 
for a short time, but not for permanent 
work. In the first case it offers the ad- 
vantage of being always ready for use, 
evolving no vapors, and when not in use 
consuming no material. It is prudent to 
protect this element from the action of the 
carbonic acid of the air by a close cover. 

The element shown in Fig. 16 has been 
patented in Germany, and is described by 
Knaffe and Kiefer,* of Vienna, as follows: 
The element consists of a combination of 
zinc and carbon. The zinc plate is 9^ 
inches long, 4^ inches wide, and of the 
thickness of pasteboard. It is amalga- 
mated according to a new process. It is 
placed between two carbon plates of equal 
size, the surface of which is twice that of 
the zinc. The carbon plates are con- 
nected with the conducting wires in such 
a manner as to prevent oxidation of the 
binding-screws and to secure constant 
contact. The zinc plate is suspended in 
a neutral salt solution in a clay cell, the 
space between the latter and the carbon 

plates being filled with pieces of coke. The consumption of 
zinc is very small. The principal advantage of this new ele- 
ment is, however, the depolarizing fluid of peculiar composition 
and powerful effect. 

The element has an electro-motive force of 1.9 volts, an in- 




* Neueste Erfindungen und Erfahrungen, vol. xviii, p. 308. 



56 



ELECTRO-DEPOSITION OF METALS. 



ternal resistance of 0.17 ohm, and a constancy such as seldom 
is attained with primary elements, 1 volt ampere lasting for IOO 
hours. 

A few words may be added in regard to plunge or bichromate 
batteries, which may be constructed for the different kinds of 
elements. For our purpose it will suffice to mention the 
Bunsen plunge battery, shown in Fig. 17. For constructive 
reasons only one fluid is used, into which the zinc as well as 

Fig 17. 




the carbon plates dip, a solution of chromic acid prepared by 
dissolving 10 parts of bichromate of potash and y 2 part of mer- 
curic sulphate in 100 parts of water, and adding 18 parts of 
pure concentrated sulphuric acid, being employed. More ad- 
vantageous is a solution of chromic acid in the form of powder 
in water, in the proportion of 1:5, for the same reason as 
given on p. 44. 

Fig. 18 shows a bichromate battery as constructed by Fein. 
Into the 6 element vessels standing in two rows in the wooden 



SOURCES OF CURRENT. 



57 



box M dip the zinc and carbon plates, which are secured to 
wooden cross-pieces provided with handles, and may be main- 
tained at any desired height by the notches e in the standard G. 
According to the current-strength required, the plates are 
allowed to dip in more or less deeply. 

Fig. 19 shows a bichromate battery as constructed by Keiser 
& Schmidt. 

In using the above-mentioned chromic acid solution first 



Fig. 1 




recommended by Bunsen, the elements first developed a very 
strong current, which, however, in a comparatively short time 
becomes weaker and weaker. The current-strength can be in- 
creased by adding at intervals a few spoonfuls of pulverized 
chromic acid to the chromic acid solution, which, however, 
finally remains without effect, when the battery has to be freshly 
filled. Hence, these batteries are not suitable for electro- 
plating operations requiring a constant current for some time. 



58 



ELECTRO- DEPOSITION OF METALS. 



For temporary use, for instance by gold-workers and others, 
for gilding or silvering small articles, the bottle- form of the 
bichromate element (Fig. 20) may be advantageously em- 
ployed. In the bottle A two long strips of carbon united above 
by a metallic connection are fastened parallel to one another 
to a vulcanite stopper, and are there connected with the bind- 
ing-screw; these form the negative element, and pass to the 
bottom of the bottle. Between them is a short thick strip of 
zinc attached to a brass rod passing stiffly through the centre 
of the vulcanite cork, and connected with the binding-screw. 



Fig. 19. 



Fig. 20. 





The zinc is entirely insulated from the carbon by the vulcanite, 
and may be drawn out of the solution by means of the brass 
rod as soon as the services of the element are no longer re- 
quired. 

This bichromate element is excellent for purposes requiring 
strong currents, where long action is not necessary. As this 
element readily polarizes, it cannot be advantageously employed 
continuously for any considerable period of time. It becomes 
depolarized, however, when left for some time on open circuit. 
The element gives an electro-motive force of about 1.9 volts. 



SOURCES OF CURRENT. 



59 



In Stoehrer's element (Fig. 21) two acids, dilute sulphuric 
acid and concentrated nitric acid, are used. The porous clay 
cell is omitted, the massive carbon cylinders K, K, etc., being 
provided with a cavity reaching almost to the bottom, which is 
filled with sand and nitric acid. The contact of the carbon and 
zinc cylinders is prevented by glass beads imbedded in the 
carbon cylinders. 

Fig. 21. Fig. 22. 





Fig. 22 shows a plunge element manufactured by Dr. G. Lang- 
bein & Co., at Leipzig-Sellerhausen, Germany, the details of 
which will readily be understood without further description. 
The zinc plates dip into the diaphragms, which are filled with a 
mixture of 26 lbs. of water and 2 lbs. of sulphuric acid free 
from arsenic in which 2^ ozs. of amalgamating salt have pre- 
viously been dissolved. The carbon plates dip into the glass 
vessels, which contain a solution of commercial crystallized 



60 ELECTRO-DEPOSITION OF METALS. 

chromic acid in water in the proportion of I part acid to 9 
water. In place of this pure chromic acid solution the follow- 
ing mixture may also be used : 

Water 10 parts by weight, sodium dichromate 1.5 parts by 
weight, pure sulphuric acid of 66° Be. 3 parts by weight. 

This solution shows no inclination towards crystallization. 
In the illustration only two elements are combined to a battery, 
but in the same manner a plunge battery of four or eight ele- 
ments may be constructed, the separate elements of which may 
all be coupled parallel, as well as one after the other, and in 
mixed groups. 

B. Thermo- Electric Piles. 

Though thermo-electric piles are only used in isolated cases 
for electro-plating operations, for the sake of completeness 
their nature and best-known forms will be briefly mentioned. 

In the year 1822, Professor Seebeck, of Berlin, discovered a 
new source of electricity, namely, inequality of temperature 
and conducting power in different metals, or in the same metal 
in different states of compression and density. When two 
pieces of different metals, connected together at each end, have 
one of their joints more heated than the other, 
an electric current is immediately set up. Of ' 23 ' 

all the metals tried, bismuth and antimony 
form the most powerful combination. 

In Fig. 23 Bm represents a bar of bismuth, 
and mS a bar of antimony soldered to the bis- 
muth bar. By leading wires from B and 5 to 
a galvanoscope, G, and heating the point of 
junction m, the needle of the galvanoscope is 
deflected. From this it may be concluded 
that an electric current circulates in the closed 
circuit GB mSG. By a closer examination 
the direction of the current may be recog- I 
nized, it flowing on the heated point of junction from the bis- 
muth to the antimony, and in the connecting wire of the ends 




SOURCES OF CURRENT. 



of the rods which remain cold, from the antimony to the bis- 
muth. The current is the stronger the greater the difference 
in the temperature of the point of junction and the free ends of 
the bars. Hence the electric current will be especially strong 
when the place of junction is heated and the ends B and 5 are 
at the same time cooled off. A combination as above de- 
scribed is called a the,rmo -electric couple, and the electricity ob- 
tained in this manner thermo-electricity . By a suitable combi- 
nation of several or many of such couples, a thermo-electric 
pile is obtained. 

Noe's thermo-electric pile (Fig. 24) consists of a series of 

Fig. 24. 





small cylinders, composed of an alloy of $6% parts of zinc and 
623^2 parts of antimony for the positive element, and stout 
German silver as the negative element. The junctions of the 
elements are heated by small gas-jets, and the alternate junc- 
tions are cooled by the heat being conducted away by large 
blackened sheets of thin copper. A pile of twenty pairs has 
an electro-motive force of 1.9 volts. 

Clamond's thermo-electric pile (Fig. 25) consists of an alloy 
of 2 parts antimony and I of zinc for the negative metal, while 
for the positive element ordinarily tinned sheet-iron is em- 
ployed, the current flowing through the hot junction from the 



62 



ELECTRO-DEPOSITION OF METALS. 



iron to the alloy. To insure a good contact between the two 
metals a strip?of tin-plate is bent into a narrow loop at one end 
This portion is then placed in a mould and the melted alloy 
poured around it, so that it is actually imbedded in the casting. 
The pile shown in the illustration consists of five series, one 
placed above the other. Each series has ten elements grouped 
in a circle, and is insulated from the succeeding series by a 
layer of cement, composed of powdered asbestos moistened 
with a solution of potassium silicate. With the consumption 
of about 6% cubic feet of gas per hour, such a pile precipi- 



Fig. 25. 




tates 0.7 oz. of copper, which corresponds to an electro-motive 
force of about 17 amperes. 

Hauck 's thermo-electric pile. — An essential defect of Clamond's 
thermo-electric pile consists in that the junctions of the dissimilar 
metals are subjected to ready destruction by being exposed to 
the direct action of the flame. Further, it is very difficult, or 
at least inconvenient, to make repairs, since in such a case it 
may become- necessary to take the entire pile apart. Hauck 
has successfully overcome these defects by adopting the princi- 
ple of indirect heating, as well as by giving the couples a more 



SOURCES OF CURRENT. 



63 



suitable form and by improving the alloy. The couples form 
four-sided wedges, to which are attached cast-iron pieces that 
transfer the heat of the gas-burner to the couples. The electro- 
motive force of a single couple is T V that of a Daniell element. 
Fig. 26 shows a combination of two piles standing upon a com- 
mon plate, one of the piles being given in cross-section. The 
glass-vessel H, with the tube, B> G, R, /, serves as a regulator 
for the gas-pressure. The pile shown in the illustration serves 



Fig. 26. 




for the production of metallic deposits on a small scale, especi- 
ally for analytical examinations. Hauck, however, also fur- 
nishes combinations of three larger piles. 

Gulcher 's thermo-electric pile, invented in 1890, is shown in 
Fig. 27. It is arranged for gas-heating, and with a constant 
supply of gas requires a pressure-regulator. The negative 
electrodes consist of nickel and the positive electrodes of an 
antimony alloy, the composition of which is kept secret. The 



64 



ELECTRO-DEPOSITION OF METALS. 



negative nickel electrodes have the form of thin tubes and are 
secured in two rows in a slate plate, which forms the termina- 
tion of a gas conduit with a U shaped cross-section beneath it. 
Corresponding openings in the slate plate connect the nickel 
tubes with the gas conduit, the latter being connected by means 
of a rubber tube with the pipe supplying the gas. Thus the 
gas first passes into the conduits, next into the nickel tubes, and 
leaves the latter through six small holes in a soap-stone socket 
screwed in the end of each tube. On leaving these sockets the 
gas is ignited and the small blue flames heat the connecting 
piece of the two electrodes. This connecting piece consists of 

Fig. 27. 




a circular brass plate placed directly over the soap-stone socket. 
One end of it is soldered to the nickel tube, while the other 
ends, towards the top, in a socket in which are cast the positive 
electrodes. The latter have the form of cylindrical rods with 
lateral angular prolongations. To the ends of these prolonga- 
tions are soldered long copper strips secured in notches in the 
slate plate. They serve partially for cooling off and partially 
for connecting the couples. For the latter purpose each cop- 
per strip is connected by a short wire with the lower end of the 
nickel tube belonging to the next couple. When the pile is to 
be used, the gas is ignited in one place, the ignition spreading 
rapidly through the entire series of couples. In about 10 min- 
utes the junctions of the metals have attained their highest 



SOURCES OF CURRENT. 65 

temperature and the pile its greatest power, which, with a con- 
stant supply of gas, remains unchanged for days or weeks. 

In view of the couversion of the heat produced by the com- 
bustion of the gas into electricity, the useful effect of the 
thermo-electric pile can be considered only a very slight one. 
One cubic meter of ordinary coal-gas produces on an average 
5200 heat-units, hence 200 litres per hour referred to one 
second i.-gVi- 5200=0.29 heat-unit. These correspond to 
1208 volt-amperes, 1 volt-ampere being equal to 0.00024 heat- 
unit. Hence, in Giilcher's thermo-electric pile, which of all 
known thermo-piles produces the greatest useful effect, not 
much more than 1 per cent, of heat is utilized in the entire 
circuit, and about ]/ 2 per cent, in the outer circuit. 

Although thermo-electric piles may be, and are occasionally, 
used for electro-plating operations, they cannot compete with 
dynamo-electric machines driven by steam, which as regards 
the consumption of heat are at least five times more effective. 
They can only be used in place of galvanic batteries, they hav- 
ing the advantage of being more convenient to put in operation, 
more simple, cleanly, odorless, and requiring less time for 
attendance. But, on the other hand, their original cost is com- 
paratively large, it being ten to twenty times that of Bunsen 
elements. Thus, for instance, Giilcher's thermo-electric pile 
costs $37.50 in Germany, to which have to be added $5 for the 
gas-pressure regulator, if required. 

C. Magneto- and Dynamo-eleclric Machines. 

It is a well-known fact that all the early experiments and im- 
provements in dynamos were made with a view of perfecting 
an electrical machine for plating, and that the success attained 
therein was the forerunner of all the magnificent dynamo 
machines for other purposes in such general use. 

The principle of induction upon which the dynamo-electric 

machines are based has been explained on p. 23. Faraday, in 

1 83 I, made the important discovery that by moving a coil of 

wire in the presence of a magnet a current of electricity was 

5 



66 ELECTRO-DEPOSITION OF METALS. 

generated in the coil, or, vice versa, by moving the magnet and 
holding the coil stationary a like result was obtained. Thus a 
current of electricity was produced either by moving a wire in 
the presence of a stationary magnet, or by moving a magnet in 
the presence of a stationary wire. 

The intensity of the current thus obtained depends on the 
power of the magnet and on the velocity with which the mag- 
net or coil is moved through the magnetic field. Upon these 
simple facts is based the whole of the recent important develop- 
ments of electrical science. 

Before describing the various attempts made to devise some 
mechanical means whereby the different elements which pro- 
duced the temporary or momentary currents could be com- 
bined, so as to collect them, and cause them to flow in rapid 
succession, the one after the other, without interruption, it will 
be well to remember that the necessary elements for producing 
these induced electric currents are simply a bar magnet and an 
insulated coil of wire. It will also be well to remember that 
every magnet, no matter what its form, has two poles — a north 
and a south pole — and each of these poles exerts a certain 
influence in its immediate neighborhood, the space thus affected 
being termed the magnetic field ox the region of the lines of force. 
The attraction or magnetic force of these lines varies as the in- 
verse ratio of the square of the distance ; therefore, the nearer 
the magnet the greater the intensity of the magnetism. Fara- 
day proved that these lines, which he designated lines of force, 
showed by their position the direction of the magnetic force, 
and by their number its intensity. By passing a coil of wire 
through this field, so as to cause it to cut, as it were, a number 
of these lines of force, a current of electricity will be generated 
in the coil ; and if it can be so arranged that a number of these 
coils will pass in rapid succession through the magnetic field, 
we shall have a series of impulses giving us practically a con- 
tinuous stream of electricity. 

Thus a magneto-electric or dynamo-electric machine is 
simply a machine for the conversion of mechanical energy into 



SOURCES OF CURRENT. 6j 

electrical energy by means of magneto-electric induction. The 
term dynamo-electric machine is also applied to a machine by 
means of which electrical energy is converted into mechanical 
energy by means of magneto-electric induction. Machines of 
the latter class are generally called tnotors, those of the former 
generators. 

Prof. S. P. Thompson defines a dynamo-electric machine as 
follows : — 

11 A machine for converting energy in the form of mechanical 
power into energy in the form of electric currents, or, vice versa, 
by the operation of setting conductors (usually in the form of 
coils of copper wire) to rotate in a magnetic field, or by vary- 
ing a magnetic field in the presence of conductors." 

The term dynamo was first applied to such machines because 
of the form in which this machine first appeared, viz., the series- 
wound machine. It was self-acting, or required no excitement 
other than what it received by the rotation of its armature in 
the field of its magnets, or, indeed, in the field of the earth. 

A dynamo-generator, or a dynamo-electric machine proper, 
consists of the following parts: — 

i. The revolving portion, usually the armature, in which the 
electro-motive force is developed which produces the current. 

2. The field magnets, which produce the field in which the 
armature revolves. 

3. The pole pieces, or free terminals of the field magnets. 

4. The commutator, by which the currents developed in the 
armature are caused to flow in one and the same direction. In 
alternating machines and in some continuous current dynamos 
this part is called the collector, and does not rectify the currents. 

5. The collecting brushes, that rest on the commutator cylin- 
der, and take off the current generated in the armature. 

The number of such dynamo machines is legion. In each 
case the arrangement of the armature of the magnets and of the 
commutators is varied, but the principle is always the same — 
coils of insulated wire being caused to cut through magnetic 
fields, as already explained. 



68 ELECTRO-DEPOSITION OF METALS. 

The first attempt to devise an electrical machine was made 
by Pixii, who, in 1832, constructed a machine consisting of a 
permanent magnet, which he caused to revolve in front of the 
iron cores of a pair of bobbins, forming an electro-magnet. 
This invention was improved by other workers in the field of 
science, especially by Saxton and Clarke, both of whom suc- 
ceeded in producing very useful electric generators, in which 
the mechanical arrangement is the reverse of that in Pixii's — 
i. e., the magnets are fixed and the coils of wire movable. 
And it is on this plan that all the subsequent machines have 
been constructed, as affording better results than where the 
coils are stationary and the magnets movable. 

A great improvement was made in 1857, D y Dr. W. Siemens, 
of Berlin. It consisted essentially in a new form of armature, 
which, owing to its simplicity and cheapness, is still used for 
many purposes, especially for electro-plating and laboratory 
work. It is composed of a cylinder of iron in which deep 
longitudinal grooves are cut resembling in section the letter H. 
In these grooves is wound lengthwise a single coil of wire, the 
two ends of which being joined to a split tube of copper on the 
axle form the commutator, from which the current is taken off 
by brushes or springs rubbing against it. By this longitudinal 
armature the advantage is gained of cutting the greatest num- 
ber of lines of force when rotated between the poles of a series 
of adjacent magnets. 

One of the most important inventions for the construction of 
electrical machines is the ring armature by Pacinotti (i860). 
With the use of this ring armature continuous currents of the 
same direction can be produced without the assistance of a 
commutator. 

Next in order comes the important discovery made simulta- 
neously, but independently, by Dr. W. Siemens and Sir C. 
Wheatstone — a discovery which marks the transition of the 
magneto- electric machine to that type most in use at present 
— the dynamo machine, called for convenience the dynamo. 
What Siemens and Wheatstone discovered was this : That a 



SOURCES OF CURRENT. 69 

current of electricity could be generated in the coils of the 
armature by the feeble residual magnetism in the iron cores of 
the electro-magnets, and that by passing this feeble current 
round the magnets their magnetism would be strengthened, 
which in turn would produce a stronger current in the arma- 
ture, and this current would again react on the magnets, render- 
ing them more powerful, this action going on until the limit of 
saturation is attained. For it must be understood that this 
mutual accumulation cannot go on indefinitely, the magnetism 
in the iron cores cannot be intensified beyond a certain point, 
and this point depends on, and is controlled, by the scientific 
conditions on which the machine is constructed. 

Machines constructed on this principle are called, as stated, 
dynamo machines, to distinguish them from those previously 
used in which the magnets were permanently magnetized, thus 
causing the division of electric generators into two great classes, 
viz., magneto and dyjtamo machines, which are subdivided into 
two varieties — one called the continuous current machine, fur- 
nishing currents in the same direction, and the other the alter- 
nating current machine, wherein the current is rapidly reversed 
or its direction changed many times a minute. 

An essential difference between continuous and alternating 
current machines is that the former may be self-exciting, 
whereas the latter must have a separate excitor or must be a 
magneto machine. The cores of the electro-magnets, it may 
be mentioned, are of cast iron, in which there is always a feeble 
residual magnetism. It is also easier to magnetize iron than 
steel, although, when the latter is once magnetized, it retains 
its magnetism for an indefinite period. 

It is not within the province of this work to describe in detail 
all the forms of dynamos, it being sufficient for our purpose to 
discuss those which are adapted to and are used for electro- 
plating uses. If we mention the Gramme machine first, it is 
not because it is superior to other machines, but because M. 
Gramme, its inventor, was the first to utilize the idea suggested 
by Dr. Pacinotti, of using an iron ring as a revolving electro- 



70 ELECTRO-DEPOSITION OF METALS. 

magnet, which, in place of having fixed revolving poles, had 
poles which traveled continuously through the whole circum- 
ference of the ring. 

Fig. 28 shows the Gramme armature in such a way as to 
allow its construction to be seen. The core or centre of the 
ring consists of a bunch of soft iron wires. The wire system 
wound about the core is formed of different spools, the initial 
wire of which is soldered to the terminal wire of the neighboring 
spool, so that all the spools of the ring form a single uninter- 
rupted conductor. The soldered places lie all on one side of 
the ring, and are fastened to flat copper strips bent at right 
angles and insulated from one another by a non-conducting 

Fig. 28. 




mass which formsjthe commutator through which the axle 
passes. The armature revolves between the poles of the electro- 
magnets secured to the side of the machine, as shown in Fig. 
29. As the ring is revolved a current is generated and flows 
out with every change in its position. The current so made is 
carried out by wire brushes which press upon the terminal 
plates of the wires in the ring. 

In the modern Gramme dynamos (Fig. 30) for galvano- 
plastic purposes, which have to furnish a considerable volume 
of current of slight' electro-motive force, the inducting magnets 
are surrounded by broad copper bands instead of being wound 
about with copper wire, and the armature is built up of stout 



SOURCES OF CURRENT. 



71 



copper rods, because the less resistance the copper windings 
have, the greater the volume of current which is produced, 
while, vice versa, the tension increases with their resistance. 
Hence, machines for electro plating purposes, which have to 
furnish quantities of current of slight tension, are wound about 
with stout copper wire, while those for illuminating purposes, 
which must furnish currents of high tension, are wound about 
with thin copper wire. For this reason machines constructed 

Fig. 29. 




for galvano-plastic use and for nickeling, coppering, brassing, 
etc., are not suitable for illuminating purposes, and vice versa, 
machines constructed for electric lighting cannot suitably be 
employed for plating purposes. 

A disadvantage of the Gramme machine is that the only por- 
tion of the copper windings on the outside of the ring armature 
is in the magnetic field of the poles of the electro-magnets, so 
that only a comparatively small portion of the armature is ex- 



7* 



ELECTRO-DEPOSITION OE METALS. 



posed to the inductive action of the magnets. Hence, in order 
to furnish correspondingly strong currents, the ring armature 
must revolve very rapidly, the three sizes or numbers of Gramme 
machines mostly employed for galvano -plastic purposes making 
in fact from i 500 to 2000 revolutions per minute, whereby the 
bearings are more rapidly worn out than with machines run- 
ning at less speed, and, besides, more power is consumed. 
This evil led S. Schuckert, of Nuremberg, to construct a ma- 



Fjg. ;,o. 




chine in which a flat ring is successfully used as an armature, 
which stands almost entirely under the inductive influence of 
the electro-magnets. Schuckert's flat ring machine is shown in 
Fig. 31. The core of the flat ring consists of thin sheet rib- 
ands insulated one from another, whereby greater solidity is 
attained. The commutator and brushes are similar to those of 
the Gramme machine. The number of revolutions varies for 
the different size machines from 500 to 1500 per minute. It is 



SOURCES OF CUKREAT. 



73 



almost noiseless in action and is exceedingly well constructed. 
The formation of sparks on the contact surface of the brushes 
with the commutator is scarcely perceptible, which secures the 
durability of the latter. 

The building of flat-ring machines has recently been abandoned 
by the firm, and they construct now a dynamo of the drum-arm- 
ature type. In consequence of the magnetic properties of this 
dynamo, the quantity of copper upon the armature can be con- 
siderably decreased, greater working stability being thereby 
imparted to the most sensitive portion of the machine. The 

Fig. 31. 




armature is a massive cylinder of soft iron sheets, which are 
thoroughly insulated from each other. They are closely pressed 
together enclosing the axis. Parallel to the latter run upon the 
circumference a number of grooves for the reception, with 
sufficient insulation, of the covered copper wires, which are 
thereby also protected from injuries from the outside. The 
commutator consists of hard bronze, or for dynamos of higher 
current strength of electrolytic copper. 

Fein, of Stuttgart, has endeavored to overcome the defect of 
the Gramme machine in a different manner. In his machines 



74 



ELECTRO-DEPOSITION OF METALS. 



the polar extensions of the magnets M and M' (Fig. 32) are 
elongated to a sort of drum, A A, which leads into the interior 
of the armature ring, whereby the greater portion of the 
windings is also brought into the magnetic fields of the electro- 
magnets. 

The machines built by Siemens & Halske, in which the drum- 
armature invented by Hefner-Altenbeck is used, show a differ- 
ent construction from those previously described. A de- 
tailed explanation of the drum-armature would lead us too 

Fig. 32. 




far. It consists of a hollow iron cylinder, which revolves with 
the shaft, and about which the wires are wound parallel to the 
revolving axis in such a manner that no wire-windings are in 
the interior of the core (cylinder). The wire spirals wound 
about the cylinder are divided into sections, which are so con- 
nected one with another as to form a single cohering wire 
conductor. The terminal wires of the separate sections are 
connected to the segments of the commutator, so that both the 
currents generated in the wire system always meet from an 
opposite direction in two portions of the commutator opposite 



SOURCES OF CURRENT. 



75 



to one another. The commutator is constructed according to 
the Gramme system, and has, of course, as many segments as 
there are sections wound upon the cylinder. A real advantage 
of the machine is that the greater portion of the wire-windings 
of the cylinder-armature is in the magnetic field. 

Fig. 33 shows a Siemens & Halske magneto-electric machine 
with cylinder-armature. 

Two series of 25 V-shaped magnets each are placed above 
and below, so that their poles of a similar name are opposite to 



Fig. 33. 




one another, the poles of a similar name of the upper and lower 
magnets being connected one with another by arched pieces of 
soft iron. In the space thus formed between the upper and 
lower magnets, the cylinder-armature revolves, the generated 
currents being carried away from the commutator by the 
brushes R and R'. 

In Siemens & Halske's dynamo-electric machines for electro- 
metallurgical purposes (Fig. 34) the plate magnets are wound 
about with square copper rods, in smaller machines with stout 
copper wire, while instead of spirals the armature carries cop- 



76 



ELECTRO-DEPOSITION OF METALS. 



per ribands, which are connected with the commutator by 
suitably bent pieces. 

Fig. 34. 




Fig. 35 shows the Krottlinger machine cbnsttucted by Krott- 
linger, of Vienna, In consists of a strong iron base, P, from 




which rise two short cylindrical electro-magnets, M M, which 
have a semicircular shaft on the upper end N, and closely 
embrace the ring R. The standards L are cast in one piece 



SOURCES OF CURRENT. 



77 



with the base P, and carry the bearing W W. The core of the 
ring R consists of separate disks of cast iron arranged alongside 
one another upon the shaft so as to form a massive cylinder 
which is wound about with stout copper wire. The inductive 
spools of the ring are connected by means of screws with phos- 
phor-bronze plates of the commutator C. In this dynamo, 
which is of the shunt-wound type, the current generated in the 
ring does not pass first through the electro- magnets, and then 
as working current into the conductor, but the greater portion 
passes as working current from the brushes B B into the con- 
ductor to the baths, while the other comparatively smaller 
portion of current passes through the wrappings of the electro- 



Fig. 36. 





magnets MM, and excites them. As in Schuckert's machines, 
a regulator with resistance coils may be inserted in the circuit 
of the current, which allows of the generation of the current 
being controlled within quite wide limits, as may be desired. 
The advantages of this dynamo consist in the large masses of 
iron of short length with a large cross-section of the cores of 
the electro-magnets, the standards and base being made in one 
piece, and in the durable iron core of the ring. The formation 
of sparks is slight. 

The Lahmeyer dynamo, shown in Figs. 36, 37 ', and 38, in 
cross-section, open side view, and perspective exterior view, 
fulfils the three principal conditions of a good dynamo, viz., 



7» 



ELECTRO-DEPOSITION OF METALS. 



great useful effect, discharge of the current without sparks, and 
solidity of construction. Opposite to the drum-armature or 
drum-inductor of the machine stand horizontally two short, 
stout electro-magnet cores, whose ends averted from the arma- 
ture are connected by a thick iron frame carried above and 
below around the windings. This electro-magnet frame of soft 
iron is cast in one piece with the base of the machine, so that 
no resistance is offered to the lines of force by a joint, while the 
large iron cross-sections also give rise to but slight magnetic 
resistance. 

The magnetic field of the Lahmeyer machine must be con- 
sidered as a magnetic circle in so far as the lines of force, which 

Fig. 38. 




are generated by the spools in the iron everywhere contiguous 
to them, pass together through both spools, and only ramify 
outside of them in the re-conducting plates B B' . By this 
favorable disposition, a current of slight strength passing 
through the wrappings of the electro-magnets produces a 
strong excitation of the latter. 

The armature is of the Siemens cylinder type, but is com- 
posed of disks of thin, white sheet-iron insulated one from the 
other by paper. Several segments of vulcanized fibre, two of 
which form the face, serve for holding the wrappings of the 
armature. The latter consists of a single layer of stout copper 
wire, and this, in conjunction, with the symmetrical disposition 



SOURCES OF CURRENT. 



79 



which excludes the scattering of the lines of force as much as 
possible, effects a discharge of the current without sparks. 
The space visible in the side view is closed by perforated plates 
secured by screws, as seen in Fig. 38. This is a further advan- 
tage of the machine in so far that all sensitive parts are pro- 
tected from external injury. Like all dynamos of the cylinder 
or drum-type, the Lahmeyer dynamo requires a large number 
of revolutions per minute, but with the slight weight of the 
armature and the solid construction of the bearings, there is 
but little danger of the rapid wearing out of the latter. 

Fig. 39. 




Fig. 39 shows a shunt-wound dynamo constructed by Dr. G. 

Langbein & Co. 

The electro-magnet frame and the foundation plate are cast 
in one single casting of soft iron, so that no resistance is offered 
by joints in any part to the lines of force, while the large cross- 
sections of iron cause a slight magnetic resistance. 

The armature, Fig. 40, is of the drum-type, and is built up 
of round discs of soft sheet iron Which are insulated from each 



80 ELECTRO-DEPOSITION OF METALS. 

other by paper discs, and pressed together and screwed upon 
the shaft. Grooves in the circumference of the armature, which 
run parallel to the axis, serve for the reception of the armature 
winding, the latter being insulated from the armature by paste- 
board. The drum-armature is surrounded by two short, ex- 
ceedingly powerful, electro-magnet cores, arranged in vertical 
position radially opposite one to the other. Their ends pro- 
ject parallel to the circumference of the armature, and their 
sloping form prevents the jerky formation of the current, the 
latter being yielded to the commutator almost without any 
sparking. In consequence of an abundant use of cross-sections 
of copper, the degree of efficiency is an excellent one. 

The commutator is, according to the Gramme system, con- 

Fig. 40. 




structed of bronze rich in copper. The journal bearings are 
made of phosphor-bronze, and in order to decrease friction are 
highly polished, as well as the portions of the steel shaft run- 
ning in them. The journals are provided with automatic ring 
lubrication. The dynamo being in box form entirely enclosed, 
all sensitive portions are protected from injury. In conse- 
quence of the use of large cross-sections of copper upon the 
armature and the magnet-winding, the number of revolutions is 
moderate, and consequently the consumption of power and the 
wear of the journals are slight. 

It may be of interest to give here a brief resume of what 
may be called the evolution of the dynamo for plating purposes 
in the United States, with special reference to the machines 
built by the Hanson & Van Winkle Co., of Newark, N. J. 



SOURCES OF CURRENT. 



8l 



The first machine for electro-plating in the market was the 
Weston dynamo, Fig. 41, which was first manufactured in 1876. 

Fig. 41. 




Being of small dimensions, of compact form, and yielding an 
abundant current, it was well adapted to the wants of the 
electro-plater, and hence it met with pronounced success, and 
to it can be traced the sudden development of electro-plating 
and electrotyping in this country. Some of these machines 
are still in use. 



Fig. 42. 



Fig. 43. 




In 1885, the " Little Wonder" dynamo, Fig. 42, was intro- 
duced, and became very popular. In 1886, the Hanson & Van 
Winkle Co. began manufacturing the "Wonder" dynamo, Fig. 
6 



82 



ELECTRO -DEPOSITION OF METALS. 



43. It embodied many new improvements and it was thought 
perfection had been reached. However, in 1891, electrical 
science had developed so many entirely new features that the 
above-mentioned firm brought out a still more improved 
machine, the H. and V. W. dynamo. 

However, the latest improvement in plating dynamos manu- 
factured by the Hanson & Van Winkle Co., is the new H. & 
V. W. dynamo, which is shown in Figs. 44, 45, and 46. 

Fig. 44. 




This new slow-speed, iron-clad, compound-wound machine 
reaches the highest degree of excellence. The distinctive 
feature of this machine is the constuction of the field magnets 
and of the frame, which are cast in one single casting. This 
construction gives a magnetic field of much greater intensity 
than can otherwise be obtained, and entirely prevents all waste- 



SOURCES OF CURRENT. 



83 



ful induced currents in magnets and pole pieces, points of the 
greatest importance and essential to high efficiency. 

The magnetic circuit is of unusually low resistance by reason 
of its shape, its shortness and the superior quality of iron used. 

Fig. 45. 




There is no magnetism in the frame, base or shaft, as the mag- 
nets are supported at some distance from the base of the 
machine. There is, therefore, no opportunity for magnetic 
leakage, and besides the whole is enclosed by a shield or case 
of metal. 



Fig. 46. 




The regulation of the voltage is entirely automatic, holding 
a constant voltage from no load to the full capacity of the 
dynamo. This result has heretofore been accomplished by the 
use of resistance rheostats, etc., requiring constant attention, in 
case the number of square feet of surface in the vats is varied, 



84 ELECTRO-DEPOSITION OF METALS. 

which is liable to burn the work if a light load is in the tanks. 
This has been overcome by the compound winding. A saving 
in the consumption of power required is also made, as the 
machine adjusts itself immediately to whatever load is placed 
thereon, from a single piece in the vats or to the full load of the 
dynamo. 

The armature is of a drum type and is built up of thin disks, 
all of which are securely fastened to the shaft. The winding is 
a modification of the Siemens method, and the mode of con- 
necting and collecting the current from the same produces a 
current as steady as any battery could give. 

The armature is so proportioned that it has but little idle 
wire over the heads and is only wound with one layer of wire. 
The winding is done with the greatest care, and so insulated 
that there is little danger of short circuiting and burning out. 
The ends of the armature and the electrical connections are 
thoroughly covered, thereby protecting them from copper dust 
or dirt of any kind. 

The necessary voltage is secured by revolving a compara- 
tively small number of coils of wire in a powerful magnetic field, 
rather than by using a large number of coils and weak field, as 
is the usual practice. The small amount of wire on the arma- 
ture accounts in a great measure for the absence of sparking 
at the brushes. 

The commutator is insulated with mica, and is of ample length 
of surface to secure the best action and reduce the wear to a 
minimum. 

The segments are pure tempered copper, the most durable 
material known for the purpose, and when necessary may be 
removed without returning the machine to the factory. The 
shaft is made of the best crucible steel, of great diameter in its 
central part, accurately tnrned and finished in the best possible 
manner. All armatures of the same size are interchangeable. 

The slow speed of this dynamo is a most important point for 
consideration, it being run at about half the speed of other 
makes of plating machines of equal cost. 



SOURCES OF CURRENT. 85 

The journals are of generous dimensions, resting in bronze 
bearings of the finest quality. They are self-aligning and self- 
oiling, with carrier rings in each bearing. The oil wells are of 
ample size to hold enough oil for two or three months' supply. 
In this manner the bearings are automatically oiled by the 
motion of the shaft, and they require no attention beyond a 
periodical examination and renewal of oil. 

The advantages claimed by the manufacturers for this 
dynamo are as follows: 1. High efficiency ; therefore economy 
of power. 2. Current generated without any sparking at the 
brushes ; therefore steady current, and small wear of brushes 
and commutator. 3. Solidity of construction; therefore safety 
against interruptions from external injury, and no risk in trans- 
portation. 4. Accessibility of the different parts and simplicity 
of design. 5. No scattering of the lines of force; therefore no 
external magnetism or the attraction of pieces of iron, or the 
magnetizing of watches and compasses, etc. 6. Perfect regu- 
lation. 7. Self-oiling bearings. 8. Ninety-five per cent, effi- 
ciency. 9. Slow speed. 10. Self-aligning bearings. 11. Me- 
chanical perfection, 12. Works equally well with light or 
heavy load, and will do more work for the same power and first 
cost than any other make of plating machines now on the 
market. 

Direct connected motors to machines of various kinds are be- 
coming so generally used that the manufacturers of the H. & 
V. W. dynamo are now providing their dynamos with motors 
of 110 and 220 volts direct, and mounted on same base so as 
to insure greater regularity of current where owing to a dis- 
tance from the engine, slipping of belt, etc., the speed may 
show a variation of 5 to 10 per cent. 

Whenever possible, it is advisable to avoid the transmission 
of the mechanical energy to the pulley of the dynamo- machine 
by means of belts, and to use for driving the dynamo a special 
electro-motor which is supplied with current from a lighting 
circuit of a central plant. 

If an electro-motor is used, it is best to connect the generator 



86 



ELECTRO-DEPOSITION OF METALS. 



and motor directly by joining (flanging) the shafts of the two 
machines. If such a system, Fig. 47, is to be set in motion, 
the current must be successively conducted into the armature- 
winding of the motor, the magnetic field of the latter having 
been previously excited. Both of these problems are solved 
by starting-resistances of wire spirals placed in front of the 
armature of the motor, which gradually brings the tension of 
the current to the amount of the conduit or working tension. 
If the electro-motor would suddenly, without starting resist- 
ances, be coupled to the circuit of the central plant, it might 
happen that in consequence of the high induced current formed 



Fig. 47. 




by induction, the insulation of the armature wires would be 
pierced, and the machine become disabled. 

Detailed descriptions of other machines, such as the Muller, 
Mather, Elmore, Biirgin, Gulcher, etc., would needlessly 
lengthen this chapter. The great impulse which the art of 
electro-plating has in modern times received is largely due 
to the important improvements that have been made in the 
construction of dynamo-electric machines, by which mechani- 
cal energy generated by the steam-engine or other convenient 
source of power may be directly converted into electrical energy. 
Without dynamos it would be impossible to electro-plate large 
parts of machines, architectural ornaments, etc., which are thus 



SOURCES OF CURRENT. 87 

protected from the influence of the weather. They may safely 
be credited with having called into existence an important 
branch of the electro-plating art, viz., nickel-plating, and espe- 
cially the nickel-plating of zinc sheets, as well as sheets of cop- 
per, brass, steel, and tin, which would have been impossible if 
the manufacturer had to rely upon the generation of the electric 
current by batteries. The latter, at the very best, are trouble- 
some to manage ; they only give out their full power when 
freshly charged, and as the chemical actions upon which they 
rely for their power progress, they deteriorate in strength and 
require frequent additions of acids and salts to be freshly 
charged, and their use demands constant vigilance and atten- 
tion. Even when working on a small scale, it is cheapest to 
procure a small gas or other motor for driving a small dynamo, 
the lathes, and grinding and polishing machines. 

To make it possible for the manufacturer of dynamos to 
suggest the most suitable machine, the following data should 
be submitted to him : — 

1. Variety, size, and number of the baths which are to be 
fed by the machine. 

2. The average surface of the articles in the bath, or their 
maximum surface, and the metals of which they consist. 

3. Whether at one time many and at another time few arti- 
cles are suspended in the bath. 

4. The distance at which the machine can be placed from, 
the baths. 

5. The power at disposal. 

D. Secondary Elements (Accumulators). 

In the theoretical part of this treatise, the polarizing current 
has been referred to. Although the polarization of metal plates 
for the production of secondary currents had previously been 
employed by Ritter, the construction of practically useful 
accumulators was first accomplished by Plante. He found 
that lead plates dipping into dilute sulphuric acid were specially 
well adapted for the production of secondary currents, and he 



88 ELECTRO-DEPOSITION OF METALS. 

arranged the accumulators as follows: In a square glass vessel 
filled with 10 per cent, sulphuric acid solution, a large number 
of lead plates were suspended in such a way that all plates 
with even numbers, hence, 2, 4, 6, and so on, were electrically 
connected one with the other, while the plates with uneven 
numbers, hence, 1,3,5 an d so on > were also in contact with 
each other. Between the separate plates dipping in the acid 
was sufficient space to prevent them from touching one the 
other. One series of the plates served as positive, and the 
other as negative, electrodes. Now by conducting an electric 
current through the plates lead peroxide is formed upon the 
positive electrodes, and by interrupting the current and com- 
bining the series of electrodes with each other, the peroxide is 
reduced to metallic lead, and the negative lead plates are oxi- 
dized, whereby an electric discharge takes place, the secondary 
or accumulator-current passing through the metallic connection 
of the series of plates. 

For the production, in the above described manner, of cur- 
rents of high power and longer duration, the plates have to be 
suspended as closely together as possible without danger of 
contact, in order to decrease the internal resistance of the 
element as far as practicable, and also to increase the quantity 
of lead peroxide. 

However, the formation of the layer of lead peroxide upon 
the lead plates of Plante's accumulator was a slow process, and 
for this reason Faure used lead grids. The square openings in 
the negative plates are filled with a paste of litharge and sul- 
phuric acid, and the positive plates with one of minium and 
sulphuric acid. The current reduces the litharge and peroxi- 
dizes the minium. 

Plante showed that accumulators form by usage — that is to 
say that up to a certain point their capacity is greater the 
more frequently they have been charged and discharged. By 
repeated oxidation and deoxidation the lead acquires a spongy 
structure, and gradually a large mass of metal takes part in the 
reaction. The formation is accelerated by immersing the fresh 



SOURCES OF CURRENT. 89 

plate for a day or two in nitric acid diluted with its own volume 
of water. 

With well-formed accumulators from 10,000 to 20,000 cou- 
lombs can in practice be stored for each kilogramme (2.2 lbs.) 
of lead. Plante obtained still higher numbers, 40,000, or even 
60,000. As the discharge usually takes place under an electro- 
motive force of about two volts, the available energy in the 
ordinary case is 20,000 to 40,000 joules per kilogramme of 
lead. Of course this energy is expended in a longer or shorter 
time according to the strength of the current. 

In practice the capacity of an accumulator is frequently 
expressed in ampere-hours, an ampere-hour being the quantity 
of electricity which passes through the circuit in an hour, when 
the strength of the current is 1 ampere. 

1 ampere-hour = 3600 coulombs. Thus in practice from 3 
to 6 ampere-hours may be stored for each kilogramme of lead. 

It is not necessary to enter here upon a description of the 
various constructions of the lead plates, but the chemical pro- 
cesses which take place in the accumulator may be briefly 
referred to. Regarding these processes several theories have 
been advanced, for instance, by Elbs, Liebenow and Loeb, and 
others, but it has not yet been definitely settled which of these 
views is correct. There can, however, be no doubt that the 
lead sulphate which is formed by the action of the sulphuric 
acid upon the lead plays the principal role, in so far as the 
charging and discharging of the accumulator are effected only 
by the decomposition and subsequent reformation of the lead 
sulphate. 

Elbs's theory is as follows: As lead is bivalent and quadri- 
valent, after the decomposition of the lead sulphate to lead and 
sulphuric acid, the latter combines with the lead sulphate which 
remains undecomposed to lead bisulphate. This formation of 
lead bisulphate must chiefly take place on the positive elec- 
trodes, since the anion (the sulphuric acid) travels to the posi- 
tive pole, and by the action of the water the lead bisulphate is 
decomposed to lead peroxide and free sulphuric acid. 



90 ELECTRO-DEPOSmON OF METALS. 

Liebenow and Loeb assume that in charging there are 
formed, by the decomposition of the lead sulphate, sulphuric 
acid-ions, lead-ions, and by the co-operation of water, lead per- 
oxide-ions and hydrogen-ions. The anions, sulphuric acid and 
lead peroxide, travel to the positive pole, and the kations, lead 
and hydrogen, to the negative pole. However, on both the poles 
only those ions are separated for the precipitation of which the 
least work is required, or in other words, whose decomposition- 
point is lowest, which in this case are lead peroxide and lead. 
Since, however, on account of the slight solubility and dis- 

Fig. 48. 




sociation of lead salts, the ions in the immediate neighborhood 
of the electrodes would soon be exhausted, further charging 
can only take place when from the lead sulphate formed on the 
electrodes, fresh molecules are brought into solution, by the 
dissociation of which the precipitated ions are replaced, and 
charging is only finished when all the lead sulphate is dissolved 
and separated as lead peroxide and lead-sponge. With a fur- 
ther passage hydrogen-ions, which possess the next highest 
decomposition-point, are separated. The above-described 



SOURCES OF CURRENT. 9 1 

process which in charging takes place by the action of the cur- 
rent, progresses in a reverse sense when, by connecting the 
positive and negative electrodes, the discharge is rendered 
possible, whereby the accumulator-current becomes available 
for exterior work. The lead peroxide is reduced and lead and 
lead sulphate are formed, while on the negative electrode the 
lead sponge is oxidized, sulphate of lead being also formed at 
the same time. 

Fig. 48 shows a common form of an accumulator. The 
separate elecctrodes are insulated from each other by glass 
tubes, the entire system being secured by lead springs which 
press the electrodes against the glass tubes. Small accumu- 
lator cells are of glass, hard rubber or celluloid, and larger ones 
of wood lined with lead. 

The sulphuric acid used for filling should be free from 
chlorine and metallic impurities, and have a specific gravity 
of 1.2 1. 

The first charging of the accumulator should be effected 
immediately after pouring in the acid, and be continued until 
vigorous evolution of gas takes place on the positive and neg- 
ative electrodes which is generally the case in about 20 hours. 
When charging is finished the accumulator is read) 7 for work. 
Detailed directions for the management of accumulators may 
here be omitted, they being furnished by the manufacturers of 
the various systems. 

The diagram Fig. 49 shows the connections of a plant as 
installed by the Electro-Chemical Storage Battery Co., of 
New York. 

By suitable manipulation of the switches and rheostats it is 
possible to make the following connections: 1. The dynamo 
alone can be used on the baths. 2. The batteries alone can 
be used on the baths. 3. The dynamo can be used on the 
baths and the batteries charged with the excess-current, while 
at the same time steadying the dynamo current. 4. The 
dynamo and batteries can be used in multiple on the baths, 
giving a greatly increased capacity. 



92 



ELECTRO-DEPOSITION OF METALS. 



Fig. 49. 




IV. 
PRACTICAL PART. 



CHAPTER IV. 



ARRANGEMENT OF ELECTRO-PLATING ESTABLISHMENTS 
IN GENERAL. 

ALTHOUGH rules valid for all cases cannot be given, because 
modifications will be necessary according to the size and extent 
of the establishment, the nature of the articles to be electro- 
plated, and the method of the process itself, there are, never- 
theless, certain main features which must be taken into con- 
sideration in arranging every establishment, be it large or small. 
Only rooms with sufficient light should be used, since the eye 
of the operator is severely taxed in judging whether the articles 
have been thoroughly freed from fat, in recognizing the differ- 
ent tones of color, etc. A northern exposure is especially 
suitable, since otherwise the reflection caused by the rays of 
the sun may exert a disturbing influence. For larger establish- 
ments the room containing the baths should, besides side-lights, 
be provided with a sky-light, which, according to the location, 
is to be protected by curtains from the rays of the sun. 

Due consideration must be given to the frequent renewal of 
the air in the rooms. Often it cannot be avoided that the 
operations of pickling, etc., must be carried on in the same 
room in which the baths are located. Especially unfavorable 
in this respect are smaller establishments working with batteries, 
in which the vapors evolved from the latter are added to the 
other vapors, and render the atmosphere injurious to health. 

(93) 



94 ELECTRO-DEPOSITION OF METALS. 

Hence, if possible, rooms should be selected having windows 
on both sides, so that by opening them the air can at any time 
be renewed, or the baths and batteries should be placed in 
rooms provided with chimneys. By cutting holes of sufficient 
size in the chimneys near the ceilings of the rooms, the dis- 
charge of injurious vapors will in most cases be satisfactorily 
effected. 

To those working with Bunsen elements, it is recommended 
to place them in a closet varnished with asphalt or ebonite 
lacquer, and provided with lock and key. The upper portion 
of the closet should communicate by means of a tight wooden 
flue with a chimney or the open air. 

Since the baths work with greater difficulty, more slowly and 
more irregularly below a ceatain temperature, provision for the 
sufficient heating of the operating rooms must be made. Ex- 
cept baths for hot gilding, platinizing, etc., the average tem- 
perature of the plating solutions should be from 64.5 ° to 68° 
F., at which they work best; it should never be below 59 F., 
for reasons to be explained later on. Hence, for large operat- 
ing rooms such heating arrangements must be made that the 
temperature of the baths cannot fall below the minimum even 
during the night, otherwise provision for the ready restoration 
of the normal temperature at the commencement of the work 
in the morning has to be made. Rooms heated during the day 
with waste steam from the engine, generally so keep the baths 
during the winter — the only season of the year under consider- 
ation — that they show in the evening a temperature of 64. 5 to 
68° F., and if the room is not too much exposed, the tempera- 
ture, especially of large baths, will only in rare cases fall below 
59 F. For greater security the heating pipes may be placed 
in the neighborhood of the baths, but if this should not suffice 
to protect the baths from cooling off too much, it is advisable 
to locate in the operating room a steam conduit of small cross- 
section fed from the boiler and to pass steam for a few minutes 
through a coil of a metal indifferent to the plating solution sus- 
pended in the bath. In this manner baths of 1000 quarts, 



ELECTRO-PLATING ESTABLISHMENTS. 95 

which, on account of several days' interruption in the opera- 
tion, had cooled to 36 F., were in ten minutes heated to 68° 
F. For smaller baths it is better to bring a small portion of 
them in a suitable vessel to the boiling-point, over a gas flame, 
and add it to the cold bath, and if, after mixing, the tempera- 
ture of the bath is still too low, repeating the operation. 

Another important factor for the operating rooms is the con- 
venient renewal of the waters required for rinsing and cleans- 
ing. Without water the electro-deposition of metals is impos- 
sible ; the success of the process depending in the first place 
on the careful cleansing of the metallic articles to be electro- 
plated, and for that purpose water, nay, much water, hot and 
cold, is required, as will be seen in the section treating on the 
''Preparation of the Articles." Large establishments should, 
therefore, be provided with pipes for the admission and dis- 
charge of water, one conduit terminating as a rose over the 
table where the articles are freed from grease. In smaller 
establishments, where the introduction of a system of water- 
pipes would be too expensive, provision must be made for the 
frequent renewal of the cleansing water in the various vats. 

In consequence of rinsing and transporting the wet articles 
to the baths much moisture collects upon the floor of the 
operating rooms. The best material for floors of large rooms 
is asphalt, it being, when moist, less slippery than cement. A 
pavement of brick or mosaic laid in cement is also suitable, but 
has the disadvantage of cooling very much. The pavement of 
asphalt or cement should have a slight inclination, a collecting 
basin being located at the lowest point, which also serves for 
the reception of the rinsing water. Wood floors cannot be 
recommended, at least for large establishments, since the con- 
stant moisture causes the wood to rot. However, where their 
use cannot be avoided, the places where water is most likely to 
collect should be strewn with sand or saw- dust, frequently re- 
newed, or the articles when taken from the rinsing water or 
bath be conveyed to the next operation in small wooden 
buckets or other suitable vessels. 



g6 ELECTRO- DEPOSITION OF METALS. 

The operating room should be of such a size as to permit the 
convenient execution of the necessary manipulations. Of 
course, no general rule can be laid down in this respect, as the 
size of the room required depends on the number of the pro- 
cesses to be executed in it, the size and number of articles to 
be electro-plated daily or within a certain time, etc. How- 
ever, there must be sufficient room for. the batteries or dynamo, 
for the various baths, between which there should be a passage- 
way at least twenty inches wide, for the table where the arti- 
cles are freed from grease, for the lye kettle, hot-water reser- 
voir, saw-dust receptacle, tables for tying the articles to 
hooks, etc. 

The rooms used for grinding, polishing, etc., also require a 
good light in order to enable the grinder to see whether the 
article is ground perfectly clean, and all the scratches from the 
first grinding are removed. Where iron or other hard metals 
are ground with emery, it is advisable to do the polishing in a 
room separated from the grinding shop by a close board parti- 
tion ; because in the preparatory grinding with emery, which is 
done dry, without the use of oil or tallow, the air is impreg- 
nated with fine particles of emery, which settle upon the polish- 
ing disks and materials, and in polishing soft metals cause fine 
scratches and fissures which spoil the appearance of the arti- 
cles, and can be removed only with difficulty by polishing. 
Hence, all operations requiring the use of emery, or coarse 
grinding powders, should be performed in the actual grinding- 
room, as well as the grinding upon stones and scratch-brushing 
by means of rapidly revolving steel scratch brushes. Articles 
already electro-plated are, of course, scratch- brushed in the 
plating-room itself, either on the table used for freeing the 
articles from grease, or on a bench especially provided for the 
purpose. In the polishing room are only placed the actual 
polishing machines, which by means of rapidly revolving disks 
of felt, flannel, etc., and the use of polishing powders, or pol- 
ishing compositions, impart to the articles the final lustre be- 
fore and after electro-plating. The formation of dust in the 



ELECTRO-PLATING ESTABLISHMENTS. 97 

polishing rooms is generally over-estimated; it is, however, 
sufficiently serious to render necessary the separation by a 
close partition of the polishing rooms from the electro-plating 
room, otherwise the polishing dust might settle upon the baths 
and give rise to various disturbing phenomena. In rooms in 
which large surfaces are polished with Vienna lime, as, for in- 
stance, nickeled sheets, the dust often seriously affects the 
health of the polishers, especially in badly ventilated rooms, 
and in such cases it is advisable to provide an effective 
ventilator. If this cannot be done, wooden frames covered 
with packing-cloth, placed opposite the polishing disks, render 
good service ; the packing-cloth, by being frequently moist- 
ened, retaining a large portion of the polishing dust. 

For grinding lathes requiring the belt to be thrown off in 
order to change the grinding, it is best to place the trans- 
mission carrying the belt-pulleys at a distance of about three 
feet from the floor, while for lathes with spindles outside the 
bearings the transmission may be on the ceiling or wall. The 
revolving direction of the principal transmission should be such 
as to render the crossing of the belts to the grinding and pol- 
ishing machines unnecessary, otherwise the belts on account of 
the great speed will rapidly wear. out. 

Electro-plating Arrangements in Particular. 

The actual electro-plating plant consists of the following 
parts: 1. The sources of current (batteries or dynamo-electric 
machines) with auxiliary apparatus. 2. The current-conductors \ 

3. The baths, consisting of the vats, the plating solution, the 
anodes, and the conducting rods with their binding-screws. 

4. The apparatuses for cleansing, rinsing, and drying. The 
sources of current have already been discussed in Chapter III,, 
p. 35, and the laws governing the suitable coupling of the 
elements on p. 19. 

A. Arrangement with elements. — In working with elements it 
is first necessary to have a clear idea of the area of the articles 
which are to be at one time electro-plated in a bath, and of the 
7 



98 ELECTRO-DEPOSITION OF METALS. 

magnitude of the resistance opposed by the bath to the current. 
This and the size of the anodes show how many elements must 
be put together for a battery, and how the elements are to be 
coupled. Suppose we have a nickel bath which requires for 
its decomposition a current of 2.5 volts of electro-motive force 
or tension. Now since, according to p. 43, a Bunsen element de- 
velops a current of 1.88 volts, the reduction of the nickel cannot 
be effected with one such element alone, but two elements must 
be coupled for tension one after the other, whereby, leaving 
the conducting resistance of the wires out of consideration, an 
electro-motive force or tension of 2 x 1.88 = 3.76 volts is ob- 
tained, with which the decomposition of the solution can be 
effected. If, on the other hand, we have a silver bath which 
requires only y 2 volt for its decomposition, we do not couple 
two elements one after the other, because the electro-motive 
force of a single element suffices for the reduction of the silver. 
On p. 19 it has been seen that by coupling the elements one 
after the other (coupling for tension) the electro motive force 
of the battery is increased, but the quantity of current is not 
increased, and that to attain the latter the elements must be 
coupled alongside of one another (coupled for quantity). 
Hence in a group of, for instance, three elements coupled one 
after another, only one single zinc surface of the elements can 
be considered effective in regard to the quantity of current. 
Now, the larger the area of articles at the same time suspended 
in the bath is, the greater the number of such effective zinc 
surfaces of the group of elements to be brought into action 
must be; and, if for baths with medium resistance, it may be 
laid down as a rule that the effective zinc surface must be at 
least as large as the area of the articles, provided the surface of 
the anodes is at least equal to the latter, the approximate num- 
ber of elements and their coupling for a bath can be readily 
found. Let us take the nickel bath, which, as above mentioned, 
requires a current of 2.5 volts, and for the decomposition of 
which two elements must, therefore, be coupled one after the 
other, and suppose that the zinc surface of the Bunsen elements 



ELECTRO-PLATING ESTABLISHMENTS. 



99 



is 500 square centimetres, then the effective zinc surface of the 
two elements coupled one after the other will also be 500 
square centimetres; hence a brass sheet 20x25^500 centi- 
metres can be conveniently nickeled on one side with these 
two elements, or a sheet 10x25 = 250 centimetres on both sides. 
Now suppose the surface to be nickeled were twice as large, 
then the two elements would not suffice, and a second group 
of two elements, coupled one after the other, would have to be 
joined to the first group for quantity, a^ shown in Fig. 4, or 
perspectively in Fig. 50. Three times the object surface would 
require three groups of elements, and so on. 

However, this, to a certain extent, empirical determination of 

Fig. 50. 




the number of elements required for plating surfaces of definite 
measure may be abandoned, and we may avail ourselves of a 
more exact determination according to electrical values, since 
at the present time the electrical relations of the baths are 
accurately known and the performances of the elements, as well 
as of the dynamos, are specified according to current quantity 
and current tension. 

As regards the result of the process of deposition, the first 
requisite which has to be taken into account is that a sufficient 
quantity of current acts upon the surface to be plated, and the 
next that the current possesses the necessary tension for the 
decomposition of the bath. Now the current quantity which 
is required for the correct formation of the deposit upon 1 
L.otC. 



100 ELECTRO-DEPOSITION OF METALS. 

square decimeter* =10x10 centimeters f (100 square centi- 
meters) may be designated as the current-density, and in the 
plating processes described later on, the suitable current-density 
is always given. If now, for instance, this current- density for 
a nickel bath is 0.6 ampere per sq. dcm., the tension 2.5 volts 
and the largest surface to be plated in the bath 50 cm. x 20 cm. 
= 1000 sq. cm. or 10 sq. dcm. a current-strength of at least 
0.6 X 10 = 6 amperes would be required. Hence, a medium- 
large element furnishing 8 amperes would suffice if the tension 
necessary for the decomposition of the electrolyte did not 
amount to 2.5 volts. As previously stated, a Bunsen element 
furnishes about 1.8 volts, and hence, in order to obtain the 
higher tension, two elements must be coupled one after the 
other, and the excess, which would be an impediment to the 
correct formation of the deposit, has to be destroyed by the 
current-regulator to be described later on, in case it is not 
preferred to increase the object-surface. 

For silvering, the current-density amounts to 0.25 ampere, 
and, with a slight excess of potassium cyanide, the silver bath 
requires 1 volt. If now, for instance, an object surface of 55 
sq. dcm., which is about equal to 50 large tablespoons, is to be 
silvered, 55 X 0.25 = 13.75 amperes and 1 volt are required. 
Hence, two elements of 8 amperes each must be coupled along- 
side one another in order to obtain 16 amperes current-quantity, 
and the excess destroyed by the current-regulator. 

In giving these illustrations it is supposed the objects are to 
have a thick solid plating. For rapid plating and a thin deposit 
a different course has to be followed. Only a slight excess of 
electro-motive force in proportion to the resistance of the bath 
being in the above-mentioned case present, reduction takes place 
slowly and uniformly without violent evolution of gas on the 
objects, and by the process thus conducted the deposit formed 
is sure to be homogeneous and dense, since it absorbs but slight 

* 1 square decimeter (sq. dcm.) = 15.501 square inches. 
f 1 centimeter (cm.) =0.394 inch. 



ELECTRO-PLATING ESTABLISHMENTS. IOI 

quantities of hydrogen, and in most cases it can be obtained of 
sufficient thickness to be thoroughly resistant. If, however, the 
operation is to be executed rapidly and without regard to great 
solidity and thickness of the deposit, the elements have to be 
coupled so that the electro-motive force is sufficiently large for 
the current to readily overcome the resistance of the bath. This 
is attained by coupling three, four, or more elements one after 
the other, as shown in the scheme Fig. 2. However, such de- 
posits can never be homogeneous, because they condense and 
retain relatively large quantities of hydrogen. 

As regards the filling and other management of the batteries, 
the reader is referred to pp. 40 to 45, under Bunsen elements. 
Having seen how many elements are required, and how they 
have to be coupled to form a battery for certain purposes, the 
auxiliary apparatuses will be next considered. 

Only in very rare cases will it be possible to always charge a 
bath or several baths with the same object- area; and according 
to the amount of business, or the preparation of the objects by 
grinding, polishing, and pickling, at one time large, and at 
another small, areas will be suspended in the bath. Now, sup- 
pose a battery suitable for a correct deposit upon an area of, 
say five square feet, has been grouped together; and, after 
taking the articles from the bath, a charge of objects only half 
as large as before is introduced, the current of the battery will, 
of course, be too strong for this reduced area, and there will be 
danger of the deposit not being homogeneous and dense, but 
forming with a crystalline structure, the consequence of which, 
in most cases, will be slight adhesiveness, if not absolute use- 
lessness. With sufficient attention the total spoiling of the 
articles might be prevented by removing the objects more 
quickly from the bath. But this is groping in the dark, the 
objects being either taken too soon from the bath, when not 
sufficiently plated, or too late, when the deposit already shows 
the consequences of too strong a current. 

To control the current an instrument called the rheostat, cur- 
rent-regulator, resistance board, or switch board, has been con- 



102 



ELECTRO-DEPOSITION OF METALS. 



structed, which allows of the current-strength of a battery being 
reduced without the necessity of uncoupling elements. It is 
evident that the current of a battery, if too strong, can be 
weakened by decreasing the number of elements forming the 
battery, and also by decreasing the surface of the anodes, be- 
cause the external resistance is thereby increased. This coup- 
ling and uncoupling of elements is, however, not only a time- 
consuming, but also a disagreeable, labor ; and it is best to use 
a resistance board with which, by the turn of a handle, the 
desired end is attained. Figs. 51 and 52 show this instrument. 




Fig. 52. 



fTotheBqth. 




To the Bath 



Its action is based upon the following conditions : As ex- 
plained on p. 20, the maximum performance of a battery takes 
place when the external resistance is equal to the internal re- 
sistance of the battery. By increasing the external resistance, 
the performance is decreased, and a current of less intensity 
will pass into the bath when resistances are placed in the 
circuit. The longer and thinner the conducting wire is, and 
the less conducting power it possesses, the greater will be the 
resistance which it opposes to the current. Hence, the re- 
sistance board consists of metallic spirals which lengthen the 
circuit, contract it by a smaller cross-section, and by the nature 



ELECTRO-PLATING ESTABLISHMENTS. IO3 

of the metallic wire has a resistance-producing effect. For a 
slight reduction of the current, copper spirals of various cross- 
sections are taken, which are succeeded by brass spirals, and 
finally by German silver spirals, whose resistance is eleven 
times greater than that of copper spirals of the same length 
and cross-section. In Fig. 51 the conducting wire coming 
from the battery goes to the screw on the left side of the 
resistance board, which is connected by stout copper wire with 
the first contact-button on the left ; hence by placing the 
metallic switch upon the button furthest to the left, the current 
passes the switch without being reduced, and flows off through 
the conducting wire secured to the setting- screw of the switch. 
By placing the switch upon the next contact-button to the 
right, two copper spirals are brought into the circuit ; by turn- 
ing the switch to the next button, four spirals are brought into 
the circuit, and so on. By a choice of the cross-sections of 
the spirals, their length and the metal of which they are made, 
the current may be more or less reduced as desired. 

To control the reduction of the current effected by the resist- 
ance, a galvanometer is placed behind it. It consists of a mag- 
netic needle oscillating upon a pin, below which the current is 
conducted through a strip of copper, or, with weaker currents, 
through several coils of wire. The electric current deflects the 
magnetic needle from its position, and the more so the stronger 
the current is ; hence the current-strength of the battery can be 
determined by the greater or smaller deflection. 

For a weak current, such as, for instance, that yielded by two 
elements, it is of advantage to use a horizontal galvanometer 
(Fig. 53). It is screwed to a table by 
means of a few brass screws in such a po- FlG - 53- 

sition that the needle in the north position, 
which it occupies, points to o° when no 
current passes through the instrument. 
Articles of iron and steel must, of course, 
be kept away from the instrument. For 
stronger currents, it is better to combine a vertical galvanometer 




io4 



ELECTRO-DEPOSITION OF METALS. 



with the resistance board and fasten it to the same frame, as 
shown in Fig. 52. The screw of the handle of the resistance 
board is connected with one end of the copper strip of the ver- 
tical galvanometer, while the other is connected with the screw 
on the right side of the resistance board in which is secured 
the wire leading to the bath. The resistance board and gal- 
vanometer are placed in one conducting wire only, either in 
that of the anodes or of the objects ; one of these wires is 
simply cut, and the end connected to the battery is secured in 



Fig. 54. 




OCT 



n&- 



the setting-screw on the side of the resistance board marked 
" strong," while the other end which is in connection with the 
bath is secured in the setting-screw on the opposite side marked 
" weak." The entire arrangement will be perfectly understood 
from Figs. 54 and 55. 

Fig. 56 shows the Improved H. & V. W. Patent Under- 
writers' switch board or rheostat, which has twice the carrying 
capacity of any resistance board ever made for this purpose, 
it having sufficient length of wire to allow of toning down the 
highest electro-motive force used in plating, to the lowest 



ELECTRO-PLATING ESTABLISHMENTS. 



105 



figure called for, without showing heat or any unfavorable 
symptoms. By the use of this switch board, the output from 



Fig. 55. 




J 


1 





a plating room using two or more tanks can be doubled, pro- 
viding the dynamo has the current capacity. 

Fig. 56. 




All platers understand that different voltages are required to 



106 ELECTRO- DEPOSITION OF METALS. 

operate successfully different kinds of solutions, and that when 
a sufficient voltage is to be generated for a solution of the 
highest resistance, and at the same time utilized in low resist- 
ance solutions, the tank nearest the dynamo, with the customary 
method, receives the most current, and a tendency to burn 
and blacken is noticed to a marked degree. When metals 
such as silver and copper are to be deposited in connection 
with such metals as nickel and brass, a higher electro-motive 
force is required, and considerable drop in voltage is demanded 
in the lower resistance solutions so as not to blacken the work. 
With the old style switch boards this is done at a great loss of 
current and work capacity of tank. With the old style switch 
boards about the greatest carrying capacity that they will feed 
is from 25 to 35 amperes ; not over 35 amperes. This deficiency 
is due to the smallness of the resistance wire and lack of 
sufficient metal conductivity. With this switch board, three 
times the current can be conveyed without showing the least 
heat in either the resistance wires, segments, switch, or 
base-plate. 

The advantages derived from the use of a resjstance-board 
having been referred to, it remains to add a few words regard- 
ing the indications made by the galvanometer. Since the 
greater deflection of the needle depends, on the one hand, on 
the greater current-strength, and, on the other, on the slighter 
resistance of the exterior closed circuit (conducting-wires, 
baths and anodes), it is evident that a bath with slighter resist- 
ance, when worked with the same battery and containing the 
same area of anodes and objects, will cause the needle to de- 
flect more than a bath of greater resistance under otherwise 
equal conditions. Hence, the deductions drawn from the posi- 
tion of the needle for the electro-plating process are valid only 
for definite baths and definite equal conditions, but, with due 
consideration of these conditions, are of great value. Suppose 
a nickel bath to work always with the same area of objects and 
anodes, and experiments have shown that the suitable current- 
strength for this area of objects is that at which the needle 



ELECTRO -PLATING ESTABLISHMENTS. 107 

stands at 15 ; and suppose, further, that the battery has been 
freshly filled and causes the needle to deflect to 25 , then the 
switch of the resistance-board will have to be turned so far to 
the right that the needle in consequence of the interposed re- 
sistances returns to 15 . Now if, after working for some time, 
the battery yields a weaker current, the needle, by reason of 
the resistance remaining the same, will constantly retrograde, 
and has to be brought back to 15 by turning the switch to the 
left, when a current of equal strength to the former will again 
flow into the bath. This manipulation is repeated until finally 
the switch rests upon the button furthest to the left, at which 
position the current flows directly into the bath without being 
influenced by the resistances of the resistance-board. If now 
the needle retrogrades below 15 , it is an indication to the 
operator that he must renew the filling of the battery if he does 
not prefer suspending fewer objects in the bath. For this 
reduced area of objects it is no longer required for the needle 
to stand at 15 in order to warrant a correct progress of the 
electric process, since the resistance being in this case greater, 
a deflection to io°, or still less, may suffice. This example 
will make it sufficiently clear that the current-indication by the 
galvanometer is not and cannot be absolute, but that the de- 
ductions must always be drawn with due consideration to the 
conditions, namely, area of objects and of anodes, and distance 
between them. An operator to proceed safely in this respect, 
and, above all, desiring to work scientifically, will replace the 
simple galvanometer by a voltmeter, which indicates the abso- 
lute magnitude of the electro-motive force passing into the 
bath, as will be explained later on. 

It frequently happens that in consequence of defective con- 
tacts with the binding-screws of the battery, or by the conduc- 
tors of the objects and of the anodes touching one another 
(short circuit with non-insulated conducting wires), no current 
whatever flows into the bath. Such an occurrence is immedi- 
ately indicated by the galvanometer, the needle being not at all 
deflected in the first case, while in the latter the deflection will 



108 ELECTRO-DEPOSITION OF METALS. 

be entirely different from the usual one. The magnetic needle 
of the galvanometer also furnishes a means of recognizing the 
polarity of the current. If the galvanometer be placed in the 
positive conductor by securing the wire coming from the bat- 
tery in the binding-screw on the south pole of the galvano- 
meter, and the wire leading to the bath in the binding-screw on 
the north pole of the needle, the needle, according to Ampere's 
law, will be deflected in the direction of the hands of a watch, 
i. e., to the right if the observer stands so in front of the gal- 
vanometer as to look from the south pole towards the north 
pole, because the battery current flows out from the positive 
pole through the conducting wire, anodes, and fluid to the 
objects, and from these back through the object wire to the 
negative pole of the battery. If now in consequence of the 
counter-current formed in the bath by the metallic surfaces of 
dissimilar nature (see later on), and flowing in an opposite 
direction to that of the battery-current, the latter is weakened, 
the needle will constantly further retrograde from the zero point, 
and when the counter or polarizing current becomes stronger 
than the battery-current, it will be deflected 1 in an opposite 
direction as before. Hence, by observing the galvanometer 
the operator can avoid the annoying consequences of polariza- 
tion, which will be further discussed under nickeling. 

From what has been said in this chapter and in the theo- 
retical part, the rules which have to be observed in conducting 
the current will be readily understood. Since the current- 
strength is weakened by resistance, the cross-sections of the 
current-carrying wire as well as of the wires leading to the 
objects and to the anodes must be of a size corresponding to 
the current-strength, and the material selected for the wires 
should possess the highest conducting power possible. Chem- 
ically pure copper is best suited for this purpose. Some infor- 
mation for calculating the thickness of the wires will be found 
on the end of the section " Arrangement with dynamo ma- 
chines." 

The connection between the anodes of the bath and the 



ELECTRO-PLATING ESTABLISHMENTS. 109 

positive pole (anode or carbon pole) of the battery is effected 
by the positive or anode wire, while the negative or object wire 
brings the objects in the bath into metallic contact with the 
negative (zinc pole) of the battery. As previously mentioned, 
the resistance board with galvanometer is placed in one or the 
other of the wires. 

For conducting the electric current to the baths, metallic 
wires, bands, spirals, or ribbons are used. The conducting 
wires are either employed in their natural metallic state, or are 
covered with some insulating or poorly conducting substance, 
such as cotton, silk, India-rubber, gutta-percha, and various 
varnishes. It is evident that covered wires should be bare and 
clean at their extremities where they are connected with the 
battery and with the anodes and objects to be plated. Wires 
of pure, well-annealed copper possess the best conducting 
power, and should have a sectional area capable of carrying 
the maximum quantity of current without offering appreciable 
resistance. Cables should be chosen where a large volume of 
current must be carried, they being more flexible than wire of 
a large size, and can be more easily laid. 

Insulated wires may come in contact with each other with- 
out inconvenience. Such, however, is not the case with bare 
wires ; because the electricity will pass through the shortest 
circuit and will not go through the bath if the two wires are in 
metallic contact. Such contact should, therefore, be carefully 
avoided. 

Vats or tanks. — These are the vessels to hold the plating 
solutions. Their shape may be either circular, square, or 
rectangular. They should be perfectly tight, impervious to 
the solutions, and unacted upon by them. They are made of 
different materials — stoneware, glass, or porcelain vats being 
best, but they are the most fragile and expensive. 

Wooden vats must be carefully constructed, and are best 
secured at the ends by bolts and nuts, as shown in Fig. 57, 
which serve to hold the sides firmly against the end pieces. 

The vat is then coated with a mixture of equal parts of pitch 



no 



ELECTRO-DEPOSITION OF METALS. 



and rosin boiled with a small quantity of linseed oil. Another 
mixture, which has been found to afford a good protective 
covering to wood, consists of 10 parts of gutta-percha, 3 o 
pitch, and 1 y 2 each of stearine and linseed oil, melted together 
and incorporated. 

For large acid copper and nickel baths wooden vats lined with 
chemically pure sheet lead about 0.118 inch thick, and the 
seams soldered with pure lead, are quite suitable. Care must, 
of course, be taken that neither the conducting rods nor the 
articles suspended in the bath and the anodes come in contact 
with the lead lining, and therefore the conducting rods should 



Fig. 57. 




not be laid directly upon the vats, but placed upon a few thick 
strips of dry wood. Further, the anodes should be suspended 
at a sufficient distance from the lead lining, because with too 
small a distance metal from the solution is precipitated upon the 
lead lining. The latter always becomes electric, which, how- 
ever, does not matter, and if the anodes are at a greater dis- 
tance from the lead lining than the objects no metal is precipi- 
tated upon the lead lining. If for the better exhaustion of the 
baths the anodes are suspended at a slight distance from the 
sides, it is advisable to protect the lead lining with thin wooden 
boards or to insulate it by giving it two coats of asphalt-lacquer. 



ELECTRO- PLATING ESTABLISHMENTS. Ill 

However, for this purpose asphalt-lacquer prepared from the 
residues of the tar industry is not available, and a solution of 
Syrian asphalt, with a small quantity of Venetian turpentine, 
should be employed. 

Objections have frequently been made to such vats, but in 
Dr. George Langbein's establishment they have for more than 
ten years been used for nickel baths without the slightest effect 
upon the baths, and no disturbance in the working of the latter 
has ever been observed. Based upon careful investigations, 
such lead-lined vats have even been used for large copper and 
brass baths containing potassium cyanide without the slightest 
injury to the baths. If even a film of lead cyanide is formed 
upon the lead, it is insoluble in excess of potassium cyanide, and 
hence is entirely indifferent as regards the bath. However, for 
nickel baths containing large quantities of acetates, citrates and 
tartrates these lead-lined vats cannot be recommended, since 
these salts possess a certain power of dissolving lead oxide. 
Still, the use of such baths has been almost entirely aban- 
doned, and the small quantities of organic acid which occasion- 
ally serve for correcting the reaction of a nickel bath need not 
be taken into consideration. The lead-lining might be dis- 
pensed with if it were not for the difficulty of keeping wooden 
vats tight. Many plating solutions impair the swelling power 
of the wood, and with even a slight change in the temperature 
the vats become pervious, the evil in time increasing. Vats 
lined with lead, on the other hand, remain tight, and have the 
advantage that the baths can be boiled in them by means of 
steam introduced through a lead coil in the vats. 

For large baths containing potassium cyanide holders of brick 
laid in cement may also be used, or holders of boiler-plate lined 
with a layer of cement. 

A very useful vat is one of iron enameled with white acid- 
proof enamel. Such vats are made in different shapes and 
sizes up to 53^ feet long, 24 inches wide and 19 inches deep. 

For gold and other solutions an agate vessel is recom- 
mended, this material standing cyanide solutions, acids, etc. 



112 



ELECTRO-DEPOSITION OF METALS. 



The vats for heating baths are best made of enameled iron 
or of wood lined with sheet lead. Stoneware vats do not bear 
heating. 

It is advantageous to provide the narrow sides of the vats 
with semicircular notches for the conducting rods to rest in, to 
prevent their rolling away. When using stoneware vats the 
conducting rods are laid directly upon the vats. Vats of other 
material must be provided with an insulated rim of wood, or 

Fig. 58. 




No. 1, 



No. 3. 





No. 4. 



No. 2. 



the rods are insulated by pushing pieces of rubber tubing over 
their ends. According to the size of the bath, 3, 5, 7, or more 
conducting rods, best of pure massive copper, or if this is too 
expensive, of strong brass tubing with iron rods inside, are 
used. 

To secure the uniform coating of the objects with metal they 
must be surrounded as much as possible by anodes, i. e. } the 
positive pole plates of the metal which is to be deposited. For 



ELECTRO-PLATING ESTABLISHMENTS. 



113 



flat objects it suffices to suspend them between two parallel 
rows ot anodes, the most common arrangement being to place 
three rods across the bath, the two outermost of which carry 
the anodes, while the objects are secured to the centre rod. 
For wide baths five conducting rods are frequently used, but 
they should always be so arranged that a row of objects is be- 
tween two rows of anodes. The arrangement frequently seen 
with four rods across the baths, of which the outermost carry 
anodes, and the other two, objects, is irrational if the objects are 
to be uniformly plated on all sides ; because, the sides turned 
towards the anodes are coated more heavily than those sus- 
pended opposite to the other row of objects. 

For large round objects it is better to entirely surround them 
with anodes, if it be not preferred to turn them frequently, so 
that all sides and portions gradually feel the effect of the im- 
mediate neighborhood of the anodes. (See "Nickeling.") 

For objects to be plated on one side only the centre rod may 
be used for the anodes, and the two outer ones for the objects; 
the surface to be plated being, of course, turned towards the 
anodes. 

The rods carrying the anodes, as well as those carrying the 
objects, must be well connected with each other, which is 
effected by means of binding posts and screws of the improved 
orms shown in Fig. 58, Nos. 1 and 2 being rod connections 
for tanks. No. 2, or double connection, 
is a very convenient form, as it can be 
adapted to so very many changes, The 
three-way connection, No. 3, is so well 
known that it hardly needs an explana- 
tion. 

The anodes are suspended from the 
cross rods by strong hooks of the same 
metal, so that they can be entirely im- 
mersed in the bath (Fig. 59). Hooks of 
another soluble metal would contaminate 
the bath by dissolving in it, and this must be strictly avoided, 



Fig. 59. Fig. 60. 




114 ELECTRO-DEPOSITION OF METALS. 

as it would cause all sorts of disturbances in the correct 
working of the bath. In case hooks of another metal, except 
platinum, are used, the anodes must be hung so that they pro- 
ject above the surface of the liquid, and the hooks not being 
immersed are, therefore, not liable to corrosion; but the 
anodes are then not completely used up, the portion dipping in 
the solution being gradually dissolved,, whilst the portion pro- 
jecting above the fluid remains intact. Instead of wire hooks, 
strips of the same metal as the anodes and fastened to them by 
a rivet may also be used (Fig. 60). 

For suspending the objects, lengths of soft pure copper wire, 
technically called slinging wires, are used. They are simply 
suitable lengths of copper wire of a gauge to suit the work in 
hand, wire of No. 20 Birmingham wire gauge (see Appendix, 
"Useful Tables,") being generally employed for such light 
work as spoons, forks and table utensils. Wire of a larger 
diameter should be employed for large and heavy goods. The 
immersed ends of these wires becoming coated with the metal 
which is being deposited, they should be carefully set aside 
each time after use, and when the deposit gets thick it should 
be stripped off in stripping acid, and the wire afterwards an- 
nealed and straightened for future use. 

To keep the rods clean and to protect them from the fluid 
draining off from the articles when taken from the bath, it is ad- 
visable to cover them with a roof of strips of wood (A), or a 
semi-circular strip of zinc coated with ebonite lacquer; by this 
means the frequent scouring of the rods, which otherwise is 
necessary in order to secure a good contact with the hooks of 
the anodes, is done away with. 

The plating solutions, briefly called baths, will be especially 
discussed in speaking of the various electro-plating processes. It 
still remains to consider the cleansing and rinsing apparatuses. 
Every electro-plating establishment, no matter how small, re- 
quires at least one tub or vat in which the objects can be rubbed 
or brushed with a suitable agent in order to free them from 
grease. This is generally done by placing a small kettle or 



ELECTRO-PLATING ESTABLISHMENTS.. I I 5 

stoneware pot containing the cleansing materia] at the right-hand 
side of the operator alongside the vat or tub. Across the latter, 
which is half filled with water, is laid a board of soft wood cov- 
ered with cloth, which serves as a rest for the objects previously 
tied to wires. The objects are then scrubbed with a brush, or 
rubbed with a piece of cloth dipped in the cleansing agent. The 
latter is then removed by rinsing the objects in the water in the 
tub and drawing them through water in another tub. By this 
cleansing process a thin film of oxide is formed upon the metals, 
which would be an impediment to the intimate union of the 
electro-deposit with the basis-metal. This film of oxide has to 
be removed by dipping or pickling, for which purpose another 
vat or tub containing the pickle, the composition of which 
varies according to the nature of the metal, has to be provided. 
After dipping, the objects have to be again thoroughly rinsed 
in water to free them from adhering pickle, so that for the 
preparatory cleansing processes three vessels with water, which 
has to be frequently renewed, as well as the necessary pots for 
pickling solutions, have to be provided. In case the vat for 
cleansing the articles or the box-like table (see Fig. 69) is 
provided with a rose-jet, under which the objects are rinsed, 
the other vats are not required. 

After having received the electro- deposit, the objects have to 
be again rinsed in cold water, which can be done in one of the 
three vats or with the rose-jet, and finally have to be immersed 
in hot water until they have acquired the temperature of the 
latter. How the water is heated makes no difference, and 
depends on the size of the establishment. The heated objects 
are then immediately dried in a box filled with dry, fine saw- 
dust — that of maple, poplar, or other wood free from tannin 
being suitable for the purpose. 

B. Arrangement with dynamo-electric machines. — For setting 
up and running a dynamo the following rules are to be ob- 
served. It is important that the dynamo be properly placed 
and the following considerations should govern the choice of 
location. The dynamo should not be exposed to moisture nor 



Il6 • ELECTRO-DEPOSITION OF METALS. 

to the dust and dirt of the polishing room. Cleanliness is a 
necessity. A cool, well-ventilated room should be chosen. 
This is important, for a well-ventilated machine will do more 
work with less wear on parts than one unfavorably placed. 

Dynamos should be set on substantial foundations, as ab- 
sence of vibration adds to the life of machines, and insures a 
more uniform current. For the larger sizes a solid masonry 
foundation should be used, while a frame work of timber will 
answer all the requirements of the smaller sizes. When the 
dynamo is placed upon the foundation it should be carefully 
leveled and accurately lined up with the driving shaft and 
pulley of countershaft. 

The commutator is an important part and requires careful 
attention. Its surface should be kept smooth. If it should 
become roughened use No. oo sand paper, which can be 
applied while the commutator is revolving. Never use emery 
cloth. As a rule the commutator only requires to be wiped off 
with a piece of canvas. The part should be lubricated, using a 
small quantity of oil, applied with a piece of cloth, not waste. 
When the commutator is out of true, it should be turned in a 
lathe. 

The brushes should be set so that the points of contact on 
the commutator at the top and bottom are diametrically oppo- 
site, care being taken that the brushes bear evenly on the 
commutator for their full surface. A brush resting on corner 
or edge will cause sparking and cutting. After adjusting the 
brushes and obtaining proper tension, start the dynamo and 
shift the brushes on the commutator to a point where there is 
no sign of sparking. This position can always be found by 
loosening the rocker-arm and moving it to the proper point, 
when the screw in the rocker-arm should be tightened to hold 
the latter in position. 

Sparking may be caused if the brushes are not set at the 
point of commutation as above directed. Brushes should not 
be fitted to the circumference of the commutator. It is im- 
portant that the full surface of the brush should bear on the 
commutator. 



ELECTRO PLATING ESTABLISHMENTS. 117 

Dynamos should be run at a speed designated on the name 
plate, care being taken that there is no slippage of belts to the 
dynamo or from the main line to the countershaft. If it is 
necessary to change the speed, never change the pulley on the 
machine ; make the alteration elsewhere. 

Fill the bearings of the dynamo with good lubricating oil 
until it just overflows at the shaft. When properly filled it will 
run for weeks without further attention. 

Use a good quality of thin, pliable belting. If possible, 
place the dynamo in such a position that a slanting belt can be 
used, and so that the underside of the belt does the pulling. 

The armature should be frequently cleaned from copper-dust 
by means of a small bellows or other instrument. Movable 
articles of iron and" steel should be kept away from the machine 
when running, as they might be attracted by the portions of 
the machine which have become strongly magnetic. 

The object- and anode-wires must be insulated from each 
other, as well as from the ground and damp brick-work by dry 
wood or porcelain, and the places of junction kept bright. 

The employment of special wire-carriers, of the form shown 

in Fig;. 61, is advisable. They consist of cast- 

& J Fig. 61. 

iron arms, provided on the ends with a case, 

between the lower and upper cover of which 

are disks of hard rubber. 

For the regulation of the current, resistance 
boards or rheostats are used, They are con- 
structed according to the same principles as 
those described under " Arrangements with 
Elements" (p. 97), only the spirals are longer and of a larger 
cross-section, and the entire instrument is stronger. Instead 
of upon wood the contact-buttons are mounted upon slate 
plates, as wood would be carbonized by the spirals becoming 
hot. 

In case one machine has to feed several baths of dissimilar 
nature and composition, the regulation of the current for all 
the baths in the main conducting wire is not feasible on ac- 




Il8 ELECTRO-DEPOSITION OF METALS. 

count of the different resistances, and it will be necessary to 
place a rheostat in front of every tank. With the use of a 
shunt-wound dynamo of the Langbein or Lahmeyer type it will 
be further necessary to place a rheostat (the rheostat of the 
dynamo) in the field of the machine itself, in order to be 
enabled to generate more or less current, as may be required, 
and to avoid an unnecessary consumption of power. From the 
scheme Fig. 62 of such a machine, with the auxiliary apparatus, 
the main conducting wire, and a few baths, the reader will 
readily see what is required. 

The dynamo rheostat will have to be placed so that the ma- 
chine yields somewhat more current than with due considera- 
tion to the object area is required for all the baths, while the 
supply of current for each vat is regulate"d by the rheostat 
placed in front of it. 

In the scheme Fig. 62 are sketched two additional instru- 
ments for measuring the quantity and the electro-motive force 
of the current. By the first called the amperemeter, or better 
ammeter, the whole current-strength can bedirectly read off in 
amperes, and by the other, called the voltmeter, the electro- 
motive force or tension in volts. 

The observing practical electro-plater will know that the 
character of a deposit obtained in a certain solution with a defi- 
nite area of objects to be plated depends largely upon the re- 
production of certain conditions, and especially upon the 
density of the current for the certain area to be plated. To 
reproduce such conditions it is highly important that either the 
electro motive force existing between anode and cathode, or 
the current flowing through the same, be accurately measured. 
The ordinary galvanometer is insufficient and often misleading, 
and not at all satisfactory for the actual measurement of either 
the voltage or current. It indicates only a change of polarity, 
a cause of trouble not often occurring with the use of a good 
dynamo. If it is desired to measure the actual E. M. F. ex- 
isting at the terminal of the dynamo or bath, only the very best 
voltmeters or ammeters should be used. They should be so 



ELECTRO -PLATING ESTABLISHMENTS. 
Fig. 62. 



119 




120 



ELECTRO-DEPOSITION OF METALS. 



constructed as to indicate quickly and accurately any sudden 
changes in current, and should be direct reading in volts and 
amperes, and their indications should not be subjected to 
gradual changes. A sensitive voltmeter, such as the Starrett 
improved voltmeter, shown in Fig. 63, will indicate the slipping 
of belts, short circuiting in tanks and any irregularity of 
power. These voltmeters have a scale from o to 6 volts and 
upwards. The scale is divided into 120 divisions so that each 

Fig. 63. 




division represents T -§ T of a volt and when used in connection 
with the switch board, will enable the plater to study carefully 
all the requirements that insure good results, and will give him 
the means of accurately reproducing such conditions as he has 
found by experience conducive to success. One voltmeter can 
be made to answer for a number of tanks by means of a shunt 
from which the wires run to each tank. By this arrangement, 
and in connection with the switch-boards, the voltage for each 
tank and the current passing through the tank are controlled. 



ELECTRO-PLATING ESTABLISHMENTS. 



121 



Fig. 64. 



Fig. 64 shows the little H. & V. W. voltmeter. These in- 
struments may be connected to each tank by hanging overhead 

or by screwing on the back of 
the tank, an advantage to the 
plater who is operating solu- 
tions that require different volt- 
ages. By touching the button 
the tension of current at each 
tank can be instantly deter- 
mined. The instrument is cali- 
brated with a standard voltmeter 



Fig. 6c. 




!•■■!!: ' ] ^m 

mi 




and is reliable. It cannot be left in circuit, and for this reason 
a switch is provided. 

The Weston voltmeter is also largely used. It is of the same 
general appearance as the Weston ammeter, Fig. 65. 

Whilst it will be sufficient in most cases to use a voltmeter in 
combination with a rheostat for regulating purposes, it will 
sometimes be found desirable to determine the actual amount 
of current in amperes passing through a tank. It is a funda- 
mental law of electrolysis that a certain number of amperes 
passing through a plating solution will cause a definite weight 
of metal to be deposited. So, for instance, one ampere will 



122 



ELECTRO-DEPOSITION OF METALS. 



deposit in one hour 1.106 grammes of nickel, or 4.05 grammes 
of silver. It is evident, therefore, that by means of an accurate 
ammeter, the amount of metal actually deposited can easily be 



Fig. 66. 




determined. The Weston ammeter, shown in Fig. 65, is very 
sensitive, indicating the slightest variation of current accurately 
and with absolute certainty. It is, especially for higher ranges, 
the best, the most economical, and at the same time the 



ELECTRO-PLATING ESTABLISHMENTS. 



23 



cheapest instrument in the market. Both the Weston volt- 
meter and the Weston ammeter are furnished by Hanson & 
Van Winkle Co., Newark, N. J. 

As previously mentioned, one voltmeter can be made to 
answer for a number of tanks by means of a switch, from which 
the wires run to each tank, the arrangement being shown in 
Figs. 66 and 6j. 

Fig. 66 shows the coupling of the main object-wire ( — ) and 
the main anode-wire ( + ) with the resistance-boards R l and R. 2 , 
the voltmeter V, the switch U, and the two baths. 



Fig. 67. 




In Fig. 67 the coupling is enlarged, and upon this the fol- 
lowing description is based : Suppose the main object-wire and 
anode-wire to be connected with the corresponding poles of a 
dynamo-machine or a battery, which for the sake of a clearer 
view is omitted in the illustration. The switch U consists of a 
brass handle, mounted with a brass foot, upon a board. In 
the foot is a screw, with which is connected by a 0.039-inch 
thick copper-wire one of the pole-screws of the voltmeter. 
The switch drags with spring pressure upon contact buttons 
connected by copper wire with the setting screws 1, 2, 3, 4, 5 



124 ELECTRO-DEPOSITION OF METALS. 

(upon the switch-board), which serve for the reception of the 
0.039-inch thick insulated wires I, 2, 3, 4, for measuring the 
tension, which branch off from the various vats or resistance- 
boards. The other pole-screw of the voltmeter is directly con- 
nected with the main anode-wire. From the main object- wire, 
a wire, whose cross-section depends on the strength of the 
working current, passes to the screw marked " strong" of the 
resistance-board R 1 ; the screw marked "weak" of the resist- 
ance-board R 1 is connected by a correspondingly stout wire 
with the object-wire of bath I, and at the same time with the 
binding-screw 1 of the shunt. The resistance-board R 2f of 
the bath II, is in the same manner connected with the main 
object-wire, the bath, and the binding-screw 2 of the switch ; 
also the resistance-boards R 3 and R± of the baths III and IV, 
which are not shown in the illustration. With the main anode- 
wire each bath is directly connected by conducting the current 
to an anode-rod of the bath by means of binding-screws and a 
stout copper wire, and establishing a metallic connection be- 
tween this anode-rod and the next one. However, instead of 
connecting both, the current may also be conducted from the 
main anode-wire to each anode-rod. 

In the illustration, the handle of the switch rests upon the 
second contact-button to the left, which is connected with the 
binding-screw 2 of the board. In the latter is secured the wire 
for measuring the tension of the resistance board R 2 ; and hence 
the voltmeter Fwill indicate the tension of the current in bath 
II. Suppose bath II is full of objects, and with the position of 
the switch of the resistance board at " week," as shown in the 
illustration, the voltmeter indicates 1.5 volts, while the most 
suitable tension for the bath' is 2.5 volts, the switch of the re- 
sistance board is turned to the left until the needle of the volt- 
meter indicates the desired 2.5 volts. 

By turning the switch of U to the left, so that it rests upon 
the contact-button 1, the measuring wire of bath II is thrown 
out, and the voltmeter indicates the tension in bath I. If the 
switch rests upon contact-button 3, the tension in bath III is 
indicated, and so on. 






ELECTRO-PLATING ESTABLISHMENTS. 1 25 

The various baths of a larger electro-plating establishment 
are most suitably worked in parallel coupling, i. e., each bath 
is directly fed from the main wire after the current has been 
brought to the proper degree by the resistance board. Coup- 
ling the baths one after the other whereby the current passes 
from one bath into the other is only practicable for metallurgi- 
cal purposes (gaining of metals), the baths in this case having 
the same resistance, and in each bath the same areas of objects 
and anodes are suspended, so that one bath works under the 
same conditions as the other. But it is far otherwise in electro- 
plating establishments in which nickel, copper, brass, silver, 
gold and other baths are operated whose resistances are entirely 
different. 

Fig. 68 shows the ground plan of an electro-plating establish- 
ment. NN X is a dynamo-electric machine, with 300 amperes at 
4 volts' tension. The resistance board belonging to the machine, 
which is placed in the conductor, is indicated by No. 1, and is 
screwed to the wall. The main conductors, marked — and +, run 
along the wall, from which they are separated by wood, and con- 
sist of rods of pure copper 0.59 inch in diameter. The rods are 
connected with each other by brass coupling-boxes with screws. 
From the negative pole and the positive pole of the machine to 
the object-wire and anode wire lead two wires, each 0.27 inch 
in diameter ; one end of each is bent to a flat loop and secured 
under the pole screws of the machine, while the other ends are 
screwed into the second bore of the binding-screws screwed 
upon each conductor. To the right and left of the machine the 
baths are placed ; Zn, indicating zinc bath ; Ni Ni, nickel baths, 
Kn, copper cyanide bath ; Mg, brass bath ; 5 K, acid copper 
bath; Si, silver bath; and Go, gold bath. Each of the first- 
named five baths has its own resistance board, designated by 2, 
3, 4, 5, 6. However, before reaching the acid copper bath, and 
the silver and gold baths, the current is conducted through two 
resistance boards, 7 and 8. Since these baths require a current 
of only slight electro-motive force, it is necessary to place two, 
and in many cases even three or four resistance boards, one 



126 



ELECTRO-DEPOSITION OF METALS. 



after another, unless it be preferred to feed these baths with a 
special machine of less tension. 



Fig. 68. 



//////in/ /////; /7rn / /jjjujjj /, /jjj/ /////// /y //■/ / TL 





C/2 




© M 



ECU 



V//////// r/ ;//? // 17-r// // /////////// ////.// //////// /// ///A 



ELECTRO-PLATING ESTABLISHMENTS. 1 27 

From Fig. 68 it will be seen that the current weakened by 
the resistance boards 7 and 8 serves for conjointly feeding the 
acid-copper, silver, and gold baths. Hence, practically, only 
one bath can be allowed to work at one time, as otherwise each 
bath would have to be provided with as many resistance boards 
as would be required for the reduction of the tension. For 
want of space the gold bath is placed in the sketch behind the 
silver bath ; but as their resistance is not the same, they must 
also be placed parallel. 

The coupling of the voltmeter and shunt is omitted in the 
illustration. Their arrangement will be understood from 
Fig. 66. 

L is the lye-kettle. It serves for cleansing the objects, by 
means of hot caustic potash or soda-lye, from grinding and 
polishing dirt and oil. Instead of the preparatory cleansing 
with hot lye, which saponifies the oils, the objects may be 
brushed off with benzine, oil of turpentine, or petroleum, the 
principal thing being the removal of the greater portion of the 
grease and dirt, so that the final cleansing, which is effected 
with lime paste, may not require too much time and labor. It 
is also advisable to cleanse the objects, in one way or the other, 
immediately after grinding, as the dirt, which forms a sort of 
solid crust with the oil, is difficult to soften and to remove 
when once hard. 

A table for freeing the articles from grease, Fig. 69, stands 
alongside the lye kettle. It consists of a box standing upon 
legs and is divided by four partitions into two larger and three 
smaller compartments. Boards covered with cloth are laid 
over the larger compartments upon which the objects are 
brushed with lime- paste for the final thorough freeing from 
grease. Over each of these compartments is a rose provided 
with a cock, under which the objects are rinsed with water. 
The outlets for the waste water from the large compartments 
are in the bottom of the box and are provided with valves. 
Of the smaller compartments, the one in the centre serves for 
the reception of the lime paste (see " Chemical Treatment "), 



128 



ELECTRO-DEPOSITION OF METALS. 



while the others contain each two pots or small stoneware vats 
with pickling fluid. In Fig. 68 these vats are indicated by n 
and 12. The two marked n contain dilute sulphuric acid for 
pickling iron and steel articles, while those marked 12 contain 
dilute potassium cyanide solution for pickling copper and its 
alloys, and Britannia, etc. For cleansing smaller articles, four 
men can at one time work on such a table ; but for cleansing 
larger articles only two. For an establishment which does not 

Fig. 69. 




require such a large table, one with a larger and two smaller 
compartments may be used. The advantages of such a box- 
table are that everything is handy together; that the pickle, in 
case a pot should break, cannot run over the floor of the work- 
shop ; and that the latter is not ruined by pickle dropping 
from the objects. The small box on the side of the table 
serves for the reception of the various scratch-brushes. 

Referring again to Fig. 68, between the lye-kettle L and the 
box-table, is a frame, 14, for the reception of brass and copper 



ELECTRO-PLATING ESTABLISHMENTS. I 29 

wire hooks of various sizes and shapes suitable for suspending 
the objects in the baths. 

The reservoir W, filled with water, standing in front of the 
machine, serves for the reception of the cleansed and pickled 
objects, if for some reason or another they cannot be imme- 
diately brought into the bath. 

H W is the hot water reservoir in which the plated objects 
are heated to the temperature of the hot water, so that they 
may quickly dry in the subsequent rubbing in the saw-dust box 
Sp. Before polishing the deposits, iron and steel objects are 
thoroughly dried in the drying chamber T (Fig. 68), heated 
either by steam or direct fire. By finally adding to the appli- 
ances a large table, 13, for sorting and tying the objects on the 
copper wires, and a few shelves not shown in the illustration, 
everything necessary for operating without disturbance will 
have been provided. 

If possible the plating-room should be on the ground floor 
and where it will receive the best light and ventilation, both 
being essential to good work. The room must also be pro- 
vided with facilities for obtaining water and steam, as much of 
the work in plating is in preparing the article for plating by 
scouring and rinsing, and, with convenient facilities in doing 
this, the cost is reduced and better work accomplished. Where 
a plating plant is required, provision should be made for ex- 
tension or development of trade. The dynamo should also be 
larger than absolutely necessary, as a plant can then be en- 
larged as required by adding one or more tanks, the other 
appliances remaining the same. 

Fig. 70 shows a plating-room arranged by the Hanson & 
Van Winkle Co., of Newark, N. J. The arrangement will be 
readily understood from the illustration, so that a detailed; 
description is not necessary. 

What has been said in the preceding section in regard to the 
conducting wires, vats, conducting rods, anodes, etc., also 
applies to establishments using electro-dynamo machines. 

In calculating the thickness of the conducting wires for dyna- 
9 



130 



ELECTRO DEPOSITION OF METALS. 
Fig. 70. 




ELECTRO-PLATING ESTABLISHMENTS. 131 

mos, I square millimetre (0.001 square inch) of conducting 
cross- section is to be allowed for every 3 amperes for so-called 
short circuits up to 20 metres (21.87 yards). This is valid for 
currents up to 500 amperes; for longer circuits 1 y 2 to 2 am- 
peres are calculated for the square millimetre of conducting 
cross-section. 



CHAPTER V. 

TREATMENT OF METALLIC ARTICLES. 

THE objects having to undergo both a mechanical and chem- 
ical preparation, each of them will be considered separately. 

A. Mechanical Treatment. 

I. Before electro -plating. — If the objects are not to be 
electro-plated while in a crude state, which is but rarely feas- 
ible, the mechanical treatment consists in imparting to them a 
cleaner surface by scratch- brushing, or a smoother and more 
lustrous one by grinding and polishing. It may here be ex- 
plicitly stated that scratch-brushing of electro-plated objects is 
not to be considered a part of their preparation, since such 
scratch-brushing is executed in the midst of, or after the 
electro-plating, process, its object being to effect an alteration 
of the electro-deposits in more than one direction, and not 
the cleansing of the surface of the metallic base. The follow- 
ing directions, therefore, apply only to scratch-brushing of 
objects not yet electro-plated. The scratch- brushing of electro- 
deposits will be considered later on. In regard to grinding, 
we have to deal with the subject only in so far as it relates to 
smoothing rough surfaces by the use of grinding powders 
possessing greater hardness than the metal to be ground. 
With grinding in the sense of instrument-grinding, the primary 
object of which is to provide the instrument with a cutting 
edge, we have nothing to do. 

As some platers seem to have wrong ideas regarding the 
electro-plating process, it may here be mentioned that the de- 
posit is formed exactly in correspondence with the surface of 
the basis-metal. If the latter has been made perfectly smooth 

( 132) 



TREATMENT OF METALLIC ARTICLES. 



133 



by grinding and polishing, the deposit will be of the same 
nature ; but if the basis-surface is rough, the deposits also will 
be rough. Hence it is wrong to suppose that by electro-plat- 
ing a rough surface can be converted into a lustrous one, and 
that pores or holes in the basis-metal can be filled by plating. 
In order to obtain a deposit which is to acquire high lustre by 
polishing, it is absolutely necessary to bring the basis into a 
polished state by mechanical treatment. In doing this it is not 
necessary to go so far as to produce high lustre, but fine 
scratches, which would be an impediment to attaining high 
lustre after plating, must be removed. 

Scratch-brushing may be effected either by hand or by a 



Fig. 71. 




Fig. 72. 



Fig. 73. 



Fig. 74. 



scratch- brush lathe. For hand work scratch brushes of more 
or less hard brass or steel wire, according to the hardness of the 
metal to be manipulated, are used. Various forms of brushes 
are employed, the most common ones being shown in the 
accompanying illustrations (Figs. 71 to 79). 

Fig. 78 shows a swing brush for frosting or satin finish, with 



34 



ELECTRO-DEPOSITION OF METALS. 



four knots of medium brass or steel wire, and Fig. 79 the 
plater's lathe goblet scratch-brush. 

In scratch brushing it is recommended first to remove, or at 
least to soften, the uppermost hard and dirty crust (the scale) 
by immersing the objects in a pickle, the nature of which 
depends onJ:he variety of metal, so that a complete removal of 



Fig. 75. 



Fig. 76. 



Fig. 77. 





Fig. 79. 



Fig. 78. 





all impurities and non-metallic substances may be effected by 
means of the scratch-brush in conjunction with sand, pumice- 
stone, powder, or emery. The composition of pickles will be 
given later on. Scratch-brushing is complete only when the 
article shows a clean metallic surface, otherwise the brushing 
(scouring) must be continued. Scratch-brushes must be care- 
fully handled and looked after, and their wires kept in good 
order. When they become bent they have to be straightened, 
which is most readily effected by several times drawing the 
brush, held in a slanting position, over a sharp grater such as 
is used in the kitchen. By this means the wires become dis- 
entangled and straightened out. 

Hand scratch-brushing being slow and tedious work, large 
establishments use circular scratch-brushes which are attached 



TREATMENT OF METALLIC ARTICLES. 



135 



to the spindle of a lathe. These circular brushes consist of 
round wooden cases in which, according to requirement, 1 to 
6 or more rows of wire bundles (see Fig. So) are inserted. 

Brushes with wooden cases are, however, more suitable for 
scratch-brushing deposits than for cleansing the metallic base, 
since for the latter purpose a more energetic pressure is usually 
applied, in consequence of which the bundles bend and even 
break off, if the wire is anyways brittle. For cleansing purposes 
a circular scratch-brush, which the workman can readily re- 
furnish with new bundles of wire, deserves the preference. It 
is constructed as follows: A round iron disk about 0.11 inch 
thick, and from 5 ^ to 7^ inches in diameter, is provided in the 
centre with a hole so that it can be conveniently placed upon 
the spindle of the lathe. At a distance of from 0.19 to 0.31 

Fig. 80. 




inch from the periphery of the disk, holes 0.079 to O.i I inch in 
diameter are drilled, so that between each two holes is a distance 
of 0.15 inch. Draw through these holes bundles of wire about 
3.93 inches long, so that they project an equal distance on 
both sides. Then bend the bundles towards the periphery, 
and on each side of the iron disk place a wooden disk 0.31 to 
0.39 inch thick. The periphery of the wooden disk, on the side 
next to the iron disk, should be turned semi-annular, so that 
the wooden disks when secured to the spindle press very lightly 
upon the wire bundles, and the latter remain very mobile. 
When a circular scratch-brush constructed in this manner and 
secured to the lathe is allowed to make from 1800 to 2000 
revolutions per minute, the bundles of wire, in consequence of 



I36 ELECTRO-DEPOSITION OF METALS. 

the centrifugal force, stand very rigid, but being mobile will 
give way under too strong a pressure without breaking off, and 
can thus be utilized to the utmost. When required, the iron 
disk can be refurnished with wires in less than half an hour. 
An error frequently committed is that the objects to be cleansed 
are pressed with too heavy a pressure against the wire brushes. 
This is useless, since only the sharp points of the wire are 
effective, the lateral surfaces of the bundles removing next to 
nothing from the articles. 

Brushes. — A definition of these instruments is unnecessary, 
and we shall simply indicate the various kinds suitable to the 
different operations. 

The fire-gilder employs, for equalizing the coating of amal- 
gam, a long-handled brush, the bristles of which are long and 

Fig. 81. Fig. 82. Fig. S3. 




very stiff. The electro-gilder uses a brush (Fig. 81) with long 
and flexible bristles. 

For scouring with sand and pumice-stone alloys containing 
nickel, such as German silver, which are difficult to cleanse in 
acids, the preceding brush, with smaller and stiffer bristles, is 
used. 

The gilder of watch- works has an oval brush (Fig. 82), with 
stiff and short bristles for graining the silver. 

The galvanoplastic operator, for coating moulds with black- 
lead, besides a number of pencils, uses also three kinds of 
brushes — the watchmaker's (Fig. 83), a hat brush, and a 
blacking-brush. The bronzer uses all kinds of brushes. 

Brushes are perfectly freed from adherent grease by washing 
with benzine or bisulphide of carbon. 

In large establishments engaged in electro-plating cast-iron 
without previous grinding, the use of the sand-blast in place of 



TREATMENT OF METALLIC ARTICLES. 



137 



the circular wire brush has been introduced with great ad- 
vantage. Objects with deep depressions, which cannot be 
reached with the scratch-brush, as well as small objects, which 
cannot be conveniently held in the hand and pressed against 
the revolving scratch-brush can be brought by the sand-blast 
into a state of sufficient metallic purity for the electro-plating 
process. 

Fig. 84 shows the La Pierre patent sand-blast. This appa- 

Fig. 84. 




ratus does not use steam, but is simply connected to an air- 
pressure of from 2 lbs. upward; consequently the work does 
not become clogged with the damp sand. It does away with 
the constant handling of the sand or the unsightly endless 
chain buckets, and requires less room than any apparatus for 
like purpose. 

Other types of sand-blasts are shown in Figs. 85, 86, and 87. 



38 



ELECTRO-DEPOSITION OF METALS. 



These machines are of great capacity, and all kinds of metals 
can rapidly and in large quantities be thoroughly freed from 
adhering impurities. They are arranged as follows: A reser- 
voir on top contains quartz sand or emery powder of a coarser 
or finer grain according to the harder or softer metal to be 
treated, or the desired grain of the metallic surface to be 

Fig. Sk. 




cleansed. The sand runs through a pipe, and on leaving the 
latter is, by means of a powerful air-current produced by a 
blower, hurled upon the articles. In place of an air current, a 
jet of steam may be employed for hurling the sand. For small 
articles the sand-blasts have been combined with a scouring 
drum, as shown in Fig. 87. 



TREATMENT OF METALLIC ARTICLES. 



139 



The uses to which a sand blast can be put are very numer- 
ous. The frosting or satin-finishing of silver-ware and other 
articles, engraving or stenciling of metal or glass, inlaying, re- 
moving scale or brazing, the nature of the work being governed 
by the fineness of the sand used as well as the pressure. 

If a clean metallic surface is to be given at one time to a large 
number of small articles, such as buckles, steel beads, metal 



Fig. 26. 




buttons, steel watch chains, ferrules, etc., a tumbling barrel or 
drum is frequently used. It generally consists of a cylindrical 
or polygonal box having a side door for the introduction of the 
work, together with sharp sand or emery, and is mounted hori- 
zontally on an axis furnished with a winch or pulley, so as to be 
revolved either by hand or power, as may be desired. In order 
to prevent certain objects, like hooks for ladies' dresses and 



40 



ELECTRO-DEPOSITION OF METALS. 



the like, from catching each other and accumulating into a 
mass, a number of nails or wooden pegs are fixed in the interior 
of the drum. 

For ordinary polishing the articles are brought into the 
tumbling barrels together with small pieces of leather waste 
(leather shavings) and taken out in one or two days. How- 
ever, to produce an actually good polish a somewhat more 

Fig. 87. 




complicated method has to be pursued. The articles are first 
freed from adhering scale by washing in water containing 5 per 
cent, of sulphuric acid, rinsed, and dried in a drying chamber 
or in a pan over a fire. They are next brought into the tumb- 
ling barrel together with the sharp sand, such as is used in 
glass-making, and revolved for about 12 hours, when they are 
taken from the barrel and freed from the admixed sand by sift- 
ing. They are then returned to the barrel, together with soft, 
fibrous sawdust, to free them from adhering sand, and at the 



TREATMENT OF METALLIC ARTICLES. 141 

same time to give them a smoother surface. They are now 
again taken from the barrel, freed from sawdust and returned 
to the barrel, together with leather shavings. They now re- 
main in the barrel until they have acquired the desired polish, 
which, according to the size and shape of the articles and the 
degree of polish required, may frequently take two weeks or 
more. Articles of different shapes and sizes are best treated 
together, time being thereby saved. The process is also ac- 
celerated by adding some fat oil to the leather shavings, which, 
of course, must be omitted when, after long use, the shavings 
have become quite greasy. The barrel should be filled about 
half full, otherwise the articles do not roll freely and polishing 
is retarded. On the other hand, when the barrel is less than 
half full there is danger of the articles bending, or in case they 
are hardened, for instance buckles, of breaking. 

For many purposes polishing in the tumbling barrel is of 
great advantage, since, independent of its cheapness, the sharp 
edges of the articles are at the same time rounded off. How- 
ever, with articles the edges of which have to remain sharp, the 
process cannot be employed. 

The tumbling barrel in which the articles are treated with 
sand cannot be used for polishing with leather shavings, it be- 
ing next to impossible to free it entirely from sand. The 
barrels should make from 50 to 70 revolutions per minute; if 
allowed to revolve more rapidly, the articles take part in the 
revolutions without rolling together, which, of course, would 
prevent polishing. 

The brightening of articles of iron and steel may be simpli- 
fied by using water to which 1 per cent, of sulphuric acid has 
been added. The barrel used for the purpose must, of course, 
be water-tight. By the addition of sand the process is acceler- 
ated. Nickel and copper blanks for coins are also cleansed in 
this manner. They are brought into the tumbling barrel, to- 
gether with a pickling fluid, and, when sufficiently treated, are 
taken out, rinsed, dried in sawdust, and finally stamped. 

Fig. 88 shows a form of an adjustable oblique tumbling 



142 



ELECTRO-DEPOSITION OF METALS. 



barrel, adapted to clean, smooth, brighten and polish nearly 
every variety of iron and brass goods. The simplicity and 
durability of the construction and the rapidity with which the 




Fig. 89. 



work is done, are distinct advantages. The machine can be 
used wet or dry. It is adjustable by screw and wheel to any 
working elevation up to 50 . The machine 
shown in the illustration is designed to 
carry a barrel 24 inches in diameter, but 
larger or smaller barrels can be used. 

Grinding. — For grinding the objects for 
the electro-plating process, wooden wheels 
covered with leather coated with emery of 
various degrees of fineness are almost ex- 
clusively used. The wooden wheels are 
made of thoroughly seasoned poplar in the manner shown in 




TREATMENT OF METALLIC ARTICLES. 1 43 

Fig. 89. The separate pieces are radially glued together, and 
upon each side in the centre a strengthening piece is glued and 
secured with screws, so that each segment of the wheel is con- 
nected with the strengthening piece. The centre of the wheel 
is then provided with a hole corresponding to the diameter of 
the spindle of the grinding lathe, to which it is secured by 
means of wedges. The periphery as well as the sides is then 
turned smooth. A good quality of leather previously soaked 
in water and cut into strips corresponding to the width of the 
wheel is then glued to the periphery, and still further secured 
by pins of soft wood. When the glue is dry the wheel is again 
wedged upon the spindle and the leather carefully turned ; it is 
then ready for coating with emery. 

With the use of grinding wheels of oak or walnut, covering 
with leather may be omitted and the emery can be applied 
directly to the wheels. However, leather-covered wheels are 
to be preferred since, by reason of their elasticity, better results 
in grinding are obtained than with uncovered wheels of the 
above-mentioned varieties of wood. 

For grinding soft metals, hard, impregnated felt wheels "set 
up" with glue and emery are also employed. 

For grinding profiled articles preference should be given to 
wheels without leather covering, and the grinding surface 
should be fitted to the profile of the article to be ground by 
cutting with a turning tool. 

Grinding wheels of paste-board and of cork waste have re- 
cently been introduced. The former are made by coating on 
both sides thin, round disks of paste-board with glue mixed 
with emery, and then gluing a sufficient number of such disks 
one upon the other to form a wheel of the desired width. The 
wheel is finally subjected to strong pressure under a hydraulic 
press and dried. 

The preparation of cork wheels is a trade secret, and they 
have been in the market for too short a time to allow of ex- 
pressing an opinion regarding their durability. They would 
appear to be very suitable for fine grinding, but are less 
adapted to preparatory grinding. 



144 ELECTRO-DEPOSITION OF METALS. 

For gluing with emery three different kinds of emery are 
used, a coarse quality (Nos. 60 to 80) for preparatory grind- 
ing, a finer quality (No. 00) for fine grinding, and the finest 
quality (No. cooo) for imparting lustre. The wheels thus 
coated are termed respectively " roughing wheel," "medium 
wheel," and "fine wheel." With the first the surface of the 
objects are freed from the rough crust. The coarse-grained 
emery used for this purpose, however, leaves scratches, which 
have to be removed by grinding upon the medium wheel until 
the surface of the objects shows only the marks due to the finer 
quality of emery, which are in their turn removed by the fine 
wheel. 

In most cases brushing with a circular bristle brush may be 
substituted for the last grinding, the articles being moistened 
with a mixture of oil and emery No. 000c. Care must be had 
not to execute the brushing, nor the grinding with the finer 
quality of emery in the same direction as the preceding grind- 
ing, but in a right angle to it. 

Treatment of the grinding wheels.- — The coating of the 
roughing wheels with emery is effected by applying to them a * 
good quality of glue and rolling them in dry, coarse emery 
powder. For the medium and fine wheels, however, the emery 
is mixed with the glue and the mixture applied to the leather. 
When the first coat is dry, a second is applied, and finally a 
third. The whole is then thoroughly dried in a warm place. 
Before use, a piece of tallow is held to the revolving disk for 
the purpose of imparting a certain greasiness to it, and in order 
to remove any roughness due to an unequal application of the 
emery it is smoothed by pressing a smooth stone against it. 
While the preparatory grinding upon the roughing wheel is 
executed dry, i. e., without the use of oil or fat, in fine grinding 
the objects are frequently moistened with a mixture of oil and 
the corresponding No. of emery. When the layer of emery is 
used up, the remainder is soaked with warm water and scraped 
off with a dull knife. The leather of the disks on which oil or 
tallow has been used is then thoroughly rubbed with caustic 



TREATMENT OF METALLIC ARTICLES. 



145 



lime or Vienna lime * to remove the greasiness, which would 
prevent the adherence of the layer of glue and emery to be 
applied later on. When the leather is thoroughly dry a fresh 
layer of emery may at once be applied. 

To prevent the leather from absorbing an excess of water 
when moistening the old layer of glue and emery for the pur- 
pose of softening it, it is advisable to apply moderately wet 

Fig. 90. 




clay to the layer and allow it to remain for a few hours when 
the scraping off of the emery can be readily effected. 

Grinding lathes. — For use, the grinding wheels or bobs are 
wedged upon a conical cast-steel spindle provided with a pulley 
and working in hard-wood bearings, as plainly shown in Fig. 
90. The cast-iron standards are screwed to the floor; the 
wooden bearings can be shifted forward and backward by 
wedges and secured in a determined position by a set screw, 

* Vienna lime is prepared from a variety of dolomite which is first burned, then 
slaked, and finally ignited for a few hours. It consists of lime and magnesia, and 
should be kept in well closed cans, as otherwise it absorbs carbonic acid and mois- 
ture from the air, and becomes useless. 
10 



I46 ELECTRO-DEPOSITION O* METALS. 

thus facilitating the removal of the spindle after throwing off 
the belt. The wheels being wedged upon a conical spindle 
they always run centrically. The changing of the wheels 
requires but a few seconds, and on account of the slight fric- 
tion of the points of the spindle in the wooden bearings the 
consumption of power is very slight. 

To avoid the necessity of throwing off the belt while chang- 
ing the grinding wheels, double machines (Fig. 91) are used, 
the principle of conical spindles being, however, preserved. 
The shaft is provided with loose and fast pulley and coupling 
lever. 

Fig. 91. 




Grinding is executed by pressing the surfaces to be ground 
against the face of the wheel, moving the objects constantly to 
and fro. The operation requires a certain manual skill, since, 
without good reason, no more should be ground away on one 
place than on another. Special care and skill are required for 
grinding large round surfaces. 

If the objects are not to be treated with the fine wheel, fine 
grinding is succeeded by brushing with oil and emery by means 
of circular brushes formed of bristles set in disks of wood (see 
Fig. 97)- Genuine bristles being at present very expensive, 
vegetable fibre, so-called fibres, has been successfully substi- 



TREATMENT OF METALLIC ARTICLES. 



47 



tuted for them, the wooden wheel being replaced by an iron 
case, in the bell-shaped cheeks of which the fibre- bundles are 
secured by means of strong nuts. Before use it is advisable to 
saturate the fibre-bundles with oil in order to deprive them of 
their brittleness, and thus improve their lasting quality. 

The grinding lathe (Fig. 92) is provided with such a fibre- 
brush, which can, of course, be just as well placed upon the 
conical spindles of double machines. The iron case is pro- 
vided with a conical hole corresponding exactly to the conical 
spindle, the large frictional surface preventing the turning of 
the brush upon the spindle or its running off. 



Fig. 92. 




In regard to grinding the various metals, the procedure, 
according to the hardness of the metal, is as follows: — 

Iron and steel articles are first ground upon the roughing 
wheel, then fine-ground upon the medium wheel, and finally 
upon the fine wheel, or brushed with emery with the circular 
brush. Very rough iron surfaces may first be ground upon solid 
emery wheels before being worked upon the roughing wheel. 

For depressed surfaces which cannot be reached with the 
large emery wheels, small walrus-hide wheels coated with glue 



4 8 



ELECTRO- DEPOSITION OF METALS. 



and emery are placed upon the point of the spindle of the 
polishing lathe (see Fig. 99). 

Brass and copper castings are first ground upon roughing 
wheels, which have lost part of their sharpness and will no 
longer attack iron. They are then ground fine upon the medium 
wheel, and finally polished upon cloth or felt wheels (bobs). 
(See below, under polishing.) 

Sheets of brass, German silver, and copper, as furnished by 
rolling-mills, are only brushed with emery and then polished 
with Vienna lime or rouge upon bobs. 



Fig. 93. 



Fig. 94. 





Zinc castings, as, for instance, those produced in lamp fac- 
tories, are first thoroughly brushed by means of circular 
brushes and emery, and then polished upon cloth bobs. 

Sheet zinc is only polished with Vienna lime and oil upon 
cloth bobs secured to the spindle shown in Fig. 98. 

Polishing. — As will be seen from the foregoing, polishing 
serves for making the articles ready, i. e., the final lustre is im- 
parted to them upon soft polishing wheels with the use of fine 
polishing powders. The polishing wheels or bobs of fine felt, 
shirting, or cloth, are secured to the polishing lathe, and, 



TREATMENT OF METALLIC ARTICLES. 1 49 

according to the hardness of the metal to be polished, make 
2000 to 2500 revolutions per minute. A foot-lathe, such as is 
shown in Fig. 93, makes generally not over 1800 revolutions 
per minute. Cloth bobs are made by placing pieces of cloth 
one upon another in the manner described under " Nickeling 
of sheet zinc," cutting out the centre corresponding to the 
diameter of the spindle, and securing the disks of cloth by 
means of nuts between two wooden cheeks upon the spindle of 
the polishing lathe. In place of cloth bobs, solid wheels of 
felt or wooden wheels covered with a layer of felt may be used, 
especially for polishing smooth objects without depressions, 
the fineness and softness of the felt depending on the degree of 
polish to be imparted and the hardness of the metal to be 
manipulated. 

An excellent polishing wheel is the Union canvas wheel, 
made by the Hanson & Van Winkle Co., of Newark, N. J. It 
is shown in Fig. 94. It is not glued, but by a special process 
the weight is reduced, the elasticity and flexibility are in- 
creased, and a cloth face is obtained, which combined with the 
glue, presents a surface that will hold emery better than any 
other wheel. Being of a flexible nature it easily adjusts itself 
to the irregularities of the work. No special skill is required 
to use it, and there is less tendency to "gouge" the work or 
spoil design. The wheel will do more work with one " setting- 
up," than any other. It is durable and easily kept in balance. 

Another wheel of great flexibility and elasticity is the 
walrine wheel manufactured by the same firm. On account of 
its flexibility and elasticity, combined with its hardness, it is 
recommended for hard grinding, and the fact that its face can 
be turned to any shape — at the same time preserving all the 
characteristics of hide wheels — will place it before sea-horse or 
walrus on its merits. One advantage of this wheel is its 
pliability, which allows it to adjust itself to any inequalities in 
the coat of emery, and consequently it wears evenly, and being 
lighter than any other serviceable wheel it is much less liable 
to injure lathe bearings. 



150 



ELECTRO-DEPOSITION OF METALS. 



Fig. 95 shows a substantial foot-power grinding and polish- 
ing lathe. It is noiseless and with friction- clutch attachment a 
speed of 2500 to 3000 revolutions per minute can be maintained 
without effort. There is nothing better for gunsmiths, black- 
smiths, skate grinders, locksmiths, bicycle repair shops, jewelers. 

It is so constructed as to 
be very rigid and strong 
to prevent vibration. 

Double polishing 
lathes, according to the 
American patterns (Figs. 
96 and 97), are used for 
polishing objects of not 
too large dimensions, 
while the lathe shown in 
Fig. 98 serves chiefly for 
polishing large sheets, 
the latter being placed 
upon a smooth wooden 
support which rests upon 
the knees of the work- 
man, as will be described 
later on in speaking of 
the nickeling of sheet 
zinc. 

Fig. 97 shows a double 

polishing lathe of larger 

size. It carries on one 

side a large felt wheel 

and a small brush, and 

upon the other a circular brush and a small walrus-hide buff. 

The spindle of the small polishing lathe, Fig. 96, carries a 

cloth bob. 

The lathe (Fig. 99) is manufactured by the Hanson & Van 
Winkle Co., of Newark, N. J. It is shown on a cast-iron 
pedestal, from which it can be disconnected and placed on a 




TREATMENT OF METALLIC ARTICLES. 



151 



bench, if required. It is made to run at a speed of 3000 revo- 
lutions per minute, at which speed the most satisfactory results 
are obtained with muslin buffs, etc. 

Fig. 96. 




Fig. 97. 




The lathe is made with steel spindles, hard-metal bearings, 



152 



ELECTRO-DEPOSITION OE METALS. 



and is designed for quick speeds. By reason of the distribu- 
tion of metal it runs without vibration. It stands 10 inches 
high to centre, has spindle 3 feet long, ij{ inches diameter, 
with collars on both ends of spindle. The pulley is 4 inches in 
diameter, 3^ inches face. The spindle is 1 inch in diameter 
between collars. The lathe is furnished with fast and loose 
pulleys where required. Detachable taper ends are shown, on 
which the smallest brush can be run. 



Fig. 99. 




Electrically driven grinding and polishing lathes are now 
furnished by the Hanson & Van Winkle Co., of Newark, N. J. 
The high speed at which emery and polishing wheels are run 
necessitate tight belts, heated bearings and the dirt carried by 
the belt. All this is overcome in these machines. They can 
be placed so as to secure the best light, the speed is constant, 
and no power is used in driving countershaft when not in use. 
The machines are furnished with and without stand. 



TREATMENT OF METALLIC ARTICLES. 



153 



Polishing rooms are not complete without a good glue pot. 
The pots used are often home made affairs, but the steam glue 
pots shown in Fig. 100 are so superior, and at the same time so 
low in cost, that it pays every plater to have them. Each pot 
sits in a separate heater The heaters are cast- steel chambers 
through which the steam circulates, keeping the glue at an 
even heat. These steel chambers al>o avoid all escaping steam. 



Fig. 100. 




The heaters are fitted with upright arms to support the wheel 
while " setting up " with glue. This allows the surplus glue to 
drop back into the glue pot instead of on the floor. 

The belt strapping attachment or endless belt machine shown 
in Fig. 101 is manufactured by the Hanson & Van Winkle Co., 
of Newark, N. J. The demand for machines of this character 
for polishing bicycle parts has greatly increased, and improve- 



154 



ELECTRO-DEPOSITION OF METALS. 



ments have from time to time been made, culminating in the 
present construction, which is much more solid and the adjust- 
ment of the tension of the belt can be done without interfering 
with the operator. There are fewer parts used than in previous 
machines, and with the flanged wheels that are supplied to go 
on the pulley lathe, and with the rubber endless belts from I 
to 3 inches and up to 12 feet in length, makes this machine 
available for all purposes. It is equally available to manufac- 



FlG. IOI 




turers of saddlery and carnage hardware, and on irregularly 
shaped articles that cannot be conveniently polished on a circu- 
lar wheel. 

No shop is now complete without one or more flexible shafts 
for grinding, polishing and burring. In many ways it will be 
found a profitable and economical device. For cleaning and 
grinding heavy castings, for polishing and burring all metal and 



TREATMENT OF METALLIC ARTICLES. 



155 



Fig. 102. 



glass, it is a most indispensable tool where power is or can be 
used to advantage. These shafts, Fig. 102, are made in stand- 
ard sizes, from J^-inch diameter core, suitable for very light 
work, to i^-inch core, capable of driving a 3-inch drill in iron 
or steel. 

Fig. 103 shows the flexible shaft with part of case and core cut 
away to show the method of construction. The core is built up 
by laying up or coiling very small tempered steel wires on a small 
diameter, each successive layer wound in an opposite direction 
of large wire, the ends firmly 
brazed together solid. The fit- 
tings are also attached by special 
brazing. The coil should be 
well lubricated with animal oil. 
Never use mineral oil. 

Self-acting polishing lathes for 
sheet-metal will be discussed un- 
der " Nickeling of zinc sheet." 

According to the hardness of 
the material to be polished, rouge 
(ferric oxide, colcothar), trip- 
oli, Vienna lime, etc., in the state 
of an impalpable powder, and 
generally mixed with oil, or 
sometimes with alcohol, are used 
as polishing agents. For hard . 
metals an impalpable rouge of 
great hardness (No. F of com- 
merce) is employed, for softer 
metals a softer rouge (No. F F F), or Vienna lime, tripoli, etc. 

It is of advantage to melt the rouge with stearine and a 
small quantity of tallow, and cast the mixture in moulds with 
the aid of strong pressure. The sticks thus formed are suffi- 
ciently greasy to render the use of oil superfluous. In order to 
impregnate the surface of the polishing bob with the polishing 
material, hold one of the sticks for a second against the revolv- 




56 



ELECTRO-DEPOSITION OF METALS. 



ing wheel, and then polish the objects by pressing them against 
the wheel, diligently moving them to and fro. The polishing 
bob must not be too heavily impregnated with rouge, since a 
surplus of the latter smears instead of cutting well. In polish- 
ing with Vienna lime, it is advisable to moisten the objects to 
be polished with oil, while the polishing bobs are saturated 
with the lime by holding a piece of it against them. 

Another process of polishing, called burnishing, is executed 
by means of tools usually made of steel for the first or ground- 
ing process, or of a very hard stone, such as agate or blood- 

Fig. 103. 




stone, for finishing. Burnishing is applied to the final polish- 
ing of deposits of the noble metals. 

2. Mechanical treatment during and after the electro -plating 
process. — In this connection, scratch-brushing the deposits 
will be first considered, the object of this operation being, on 
the one hand, to promote the regular formation of certain de- 
posits ; and on the other, to affect the physical properties of 
the deposits ; and, finally, to ascertain whether the deposit 
adheres to the basis-metal. 



TREATMENT OF METALLIC ARTICLES. 1 57 

If it is seen by the irregular formation of the deposit that the 
basis-metal has not been cleaned with sufficient care by the 
preparatory scratch-brushing, the object has to be taken from 
the bath and the defective places again scratch-brushed with 
the application of water and sand, or pumice-stone, when the 
object is again pickled and replaced in the bath. 

On the other hand, electro-deposited metals are always more 
or less porous, they having, so to say, a net-like structure, 
though it may not be visible to the naked eye. By scratch- 
brushing, the meshes of the net are made closer by particles of 
metals being forced into them by the brush, and the deposit is 
thus rendered capable of receiving additional layers of metal. 
Furthermore, by scratch-brushing the dull deposits acquire a 
certain lustre which is enhanced by the subsequent polishing 
process. Finally, by an unsparing application of the scratch- 
brush, it will be best seen whether the union of the deposit with 
the basis-metal is sufficiently intimate to stand, without becom- 
ing detached, the subsequent mechanical treatment in polishing. 

According to the object in view, and the hardness of the de- 
posit to be manipulated, scratch-brushes of steel or brass wire 
are chosen. For nickel, which, as a rule, requires scratch- 
brushing least, and chiefly only for the production of very thick 
deposits, steel wire of 0.2 millimetre thickness is taken ; for 
deposits of copper, brass, and zinc, brass wire of 0.2 millimetre ; 
for silver, brass wire of 0.15 millimetre; and for gold, brass 
wire of 0.07 to 0.1 millimetre. Scratch-brushing is seldom 
done dry. The tool as well as the pieces should be constantly 
kept wet with liquids, especially such as produce a lather in 
brushing, for instance, water and vinegar, or sour wine, or solu- 
tions of cream of tartar or alum, when it is desired to brighten 
a gold deposit which is too dark. However, the liquid most 
generally used is a decoction of licorice-root, of horse-chestnut, 
of marshmallow, of soap-wort, or of the bark of Panama-wood, 
all of which, being slightly mucilaginous, allow of a gentle 
scouring with the scratch-brush, with the production of an 
abundant lather. A good adjunct for scratch-brushing is a 



i 5 8 



ELECTRO-DEPOSITION OF METALS. 



shallow wooden tub containing the liquid employed, with a 
board laid across it nearly level with the edges, which, how- 
ever, project a little above. This board serves as a rest for 
the pieces. 

The hand scratch-brush, when operating upon small objects, 
is held by the workman in the same manner as a paint brush, 
and is moved over the object with a back and forward motion 

Fig. 104. 




imparted by the wrist only, the forearm resting on the edge of 
the tub. For larger objects, the workman holds his extended 
ringers close to the lower part of the scratch brush, so as to 
give the wires a certain support, and, with raised elbow, strikes 
the pieces repeatedly, at the same time giving the tool a sliding 
motion. When a hollow is met with, which cannot be scoured 
longitudinally, a twisting motion is imparted to the tool. 



TREATMENT OF METALLIC ARTICLES. 1 59 

The lathe brush (Fig. 104) is mounted upon a spindle, and is 
provided above with a small reservoir to contain the lubricating 
fluid, a small pipe with a tap serving to conduct the solution 
from this to a point immediately above the revolving brush. 
The top of the brush revolves towards the operator, who pre- 
sents the object to be scratch-brushed to the bottom. The 
brush is surrounded by a wooden cage or screen to prevent 
splashing. To protect the operator against the water projected 
by the rapid motion, there is fixed to the top of the frame a 
small inclined board, which reaches a little lower than the axis 
of the brush without touching it. This board receives the pro- 
jected liquid, and lets it fall into a zinc trough, which forms the 
bottom of the box. Through an outlet provided in one of the 
angles of the trough, a rubber tube conveys the waste liquid to 
a reservoir below. After scratch-brushing every trace of the 
lubricating liquid must be washed away before placing or re- 
placing the objects in the bath. 

The finished electro-plated objects are first rinsed in clean 
water to remove the solution constituting the bath adhering to 
them. They are next immersed in hot water, where they remain 
until they have acquired the temperature of the water, and are 
then quickly rubbed with dry, hot sawdust. It is best to use 
sawdust of soft wood, free from tannin, such as maple, poplar, 
or pine. Oak sawdust is not suitable for the purpose on ac- 
count of its content of tannin, which imparts a dirty coloration 
to the electro- deposits. Boxwood sawdust, though much used, 
is not sufficiently absorbent, and sticks to the moist objects. 
The sawdust used must be freed from coarser particles of wood 
by sifting. For holding the sawdust a zinc box with double 
bottom is frequently used, which is heated by waste steam or 
some other process. In order to remove all moisture from the 
pores it is advisable to place plated objects of iron and steel 
for a few hours in an oven heated to between 140 and 1 75 F. 
A very good method of freeing nickeled objects from all moist- 
ure which may have collected in the pores is to immerse them 
for about ten minutes in boiling linseed oil, and, after allowing 



160 ELECTRO DEPOSITION OF METALS. 

them to drain off, to remove the adhering oil by rubbing with 
sawdust. According to some electro-platers, the deposit of 
nickel thus treated loses its brittleness and will stand bending 
several times, for instance, wire, sheets, etc., without breaking. 
Experiments made by Dr. George Langbein did not confirm 
these statements, but the security against rust of the nickeled 
iron objects is found to be considerably enhanced by boiling 
in linseed oil. 

The electro-plated objects, when dry, are finely polished, 
which is effected upon polishing bobs of fine felt, cloth, or 
flannel, with the use of fine rouge, Vienna lime, tripoli, etc., or 
by burnishing. 

Nickel deposits are almost without exception polished upon 
cloth or felt bobs with rouge or Vienna lime and oil. Copper 
and brass deposits are polished with fine flannel bobs, the polish- 
ing powder being applied very sparingly. Deposits of tin are 
generally only scratch-brushed, it being impossible to impart 
great lustre to this metal by polishing with bobs. After drying, 
the deposit is polished with whiting. Deposits of gold and silver 
as well as of platinum are polished by burnishing, the steel 
burnisher being used for the grounding process, and an agate 
or bloodstone burnisher for finishing. The operation of burn- 
ishing is carried on as follows : Keep the tool continually 
moistened with soap-suds. Take hold of the tool very near to 
the end, and lean very hard with it on those parts which are to 
be burnished, causing it to glide by a backward and forward 
motion without taking it off the piece. When it is requisite 
that the hand should pass over a large surface at once without 
losing its point of support on the work bench, be careful in 
taking hold of the burnisher to place it just underneath the little 
finger. By these means the work is done more quickly, and 
the tool is more solidly fixed in the hand. The burnishers are 
of various shapes to suit the requirements of different kinds of 
work, the first rough burnishing being often done by instru- 
ments with comparatively sharp edges, while the finishing 
operations are accomplished with rounded ones. Fig. 105 



TREATMENT OF METALLIC ARTICLES. IOI 

illustrates the most common forms of burnishers of steel and 
agate. Both must be free from cracks and highly polished. 
To keep them free from blemishes they are from time to time 
polished by vigorously rubbing them with fine tin putty, rouge 
or calcined alum upon a strip of leather fastened upon a piece 
of wood which is placed in a convenient position upon the 
work bench. 

The objects polished with Vienna lime and oil, or with rouge, 
have to be freed from adhering polishing dirt, which, with flat 

Fig. 105. 




smooth objects, is effected by wiping with a flannel rag and 
Vienna lime, and in those with depressions or matted sur- 
faces by brushing with a soft brush and soap-water, and then 
drying in sawdust. 

B. Chemical Treatment. 
While it is the aim of the mechanical treatment to prepare 
a pure metallic, and at the same time a smoother, surface, the 
11 



1 62 ELECTRO-DEPOSITION OF METALS. 

chemical preparation of the objects serves, on the one hand 
the purpose of facilitating the mechanical treatment by soften- 
ing and dissolving the impurities of the surface and, on the 
other, of freeing the mechanically treated objects from adher- 
ing oil, grease, dirt, etc., so as to bring them into the state of 
absolute purity required for the electro-plating process. 

Pickling and dipping. The composition of the pickling 
liquor varies according to the nature of the metal to be treated. 

Cast-iron and wrought-iron articles are pickled in a mixture 
of I part by weight of sulphuric acid of 66° Be. and 15 parts 
by weight of water.* 

To cleanse badly rusted iron articles without attacking the 
iron itself, it is recommended to pickle them in a concentrated 
solution of chloride of tin, which, however, should not contain 
too much free acid, as otherwise the iron is attacked. Bucher 
recommends a pickle composed as follows: Dissolve 3*^ ozs. 
of chloride of tin in 1 quart of water, and \yi drachms of tar- 
taric acid in 1 quart of water. Pour the former solution into 
the latter, and add 20 cubic centimeters of indigo solution 
diluted with 2 quarts of water. The object of the addition of 
indigo is not plain. 

An excellent pickle for iron is also obtained by mixing 10 
quarts of water with 28 ozs. of concentrated sulphuric acid, dis- 
solving 2 ozs. of zinc in the mixture, and adding 12 ozs. of 
nitric acid. This mixture makes the iron objects bright, while 
in dilute sulphuric or hydrochloric acid they become black. 

For many cases pickling may advantageously be effected in 
the electrolytic way. Suspend the articles in a weak acid bath 
(hydrochloric or sulphuric acid), connect them with the posi- 
tive pole of a source of current, and suspend opposite to them 
a sheet of metal (copper or brass), which is connected with 
the negative pole. 

The duration of pickling depends on the more or less thick 
layer of scale, etc., which is to be removed or softened. The 

* The acid should be poured into the water; not the water into the acid. 



TREATMENT OF METALLIC ARTICLES. 1 63 

process may be considerably assisted and the time shortened by 
frequent scouring with sand or pumice. The pickled articles 
are rinsed in cold water, then immersed in hot water, and dried 
in sawdust. In order to neutralize the acid remaining in the 
pores, it is advisable to make the rinsing water alkaline by the 
addition of caustic potash or soda, etc. 

Zinc objects are only pickled when they show a thick layer 
of oxide, in which case pickling is also effected in dilute sul- 
phuric or hydrochloric acid, and brushing with fine pumice. A 
very useful pickle for zinc consists of sulphuric acid 100 parts 
by weight, nitric acid 100, and common salt 1. The zinc ob- 
jects are immersed in the mixture for one second, and then 
quickly rinsed off in water which, should be frequently changed. 

Copper, and its alloys brass, bronze, tombac, and German silver, 
are cleansed and brightened by dipping in a mixture of nitric 
acid, sulphuric acid, and lampblack, a suitable pickle consisting 
of sulphuric acid, of 66° Be., 50 parts by weight, nitric acid, of 
36 Be., 100, common salt 1, and lampblack 1. In order to 
remove the brown coating, due to cuprous oxide, the objects 
are first pickled in dilute sulphuric acid, and then dipped for a 
few seconds, with constant agitation, in the above-mentioned 
pickle until they show a bright appearance. They are then 
immediately rinsed in water to check any further action of the 
pickle. 

If objects of copper or its alloys are not to be subjected, after 
pickling, to further mechanical treatment, or are to be at once 
placed in the electro-plating bath, it is best to execute the pick- 
ling process in two operations by treating them in a preliminary 
pickle and brightening them in the bright-dipping bath. The 
preliminary pickle consists of nitric acid, of 3 6° Be., 200 parts 
by weight, common salt 1, lampblack 2. In this preliminary 
pickle the articles are allowed to remain until all impurities are 
removed, when they are rinsed in a large volume of water, 
dipped in boiling water, so that they quickly dry, and plunged 
into the bright- dipping bath, which consists of nitric acid, of 40 
Be., 75 parts by weight, sulphuric acid, of 06° Be., 100, and 



1 64 ELECTRO-DEPOSITION OF METALS. 

common salt I. It is not advisable to bring the objects which 
have passed through the preliminary pickle and rinsing water 
directly, while still moist, into the bright-dipping bath, since for 
the production of a beautiful pure lustre the introduction of 
water into the bright-dipping bath must be absolutely avoided. 

Hence the objects treated in the preliminary pickle should 
first be dried by heating in hot water, shaking the latter off. 

Potassium cyanide, dissolved in ten times its weight of water, 
is often used instead of the acid pickle for brass, especially when 
it is essential that the original polish upon the objects should 
not be destroyed, as in the preparation of articles for nickel- 
plating. The objects should remain in this liquid longer than 
in the acid pickle, because the metallic oxides are far less 
soluble in this than in the latter. In all cases the final clean- 
ing in water must be observed. 

All acid pickles used for different kinds of work should be 
kept distinct from each other, so that one metal may not be 
dipped into a solution containing a more electro-negative metal, 
which would deposit upon it by chemical exchange. 

The pickled objects must not be unnecessarily exposed to the 
air, and should be transferred as quickly as possible from the 
pickle to the wash-waters, and then to the electro-plating bath, 
or, if this is not feasible, kept under pure water. Pickled ob- 
jects which are not to be plated are carefully washed in 
water, which should be frequently changed, rinsed, drawn 
through a solution of tartar, and dried by dipping in hot water 
and rubbing with saw-dust. 

Places soldered with soft solder, as well as parts of iron, be- 
come black by pickling, and have to be brightened by scour- 
ing with pumice, or by scratch-brushing. 

Matting. It is frequently required that objects of brass or 
other alloys of copper should be given a dead surface so that 
after plating they show a beautiful matt lustre. Beautiful 
effects may by this means be obtained, especially in the bronze 
ware industry. Matting may be effected in various ways, 
either chemically, mechanically, or by galvanoplasty. 



TREATMENT OF METALLIC ARTICLES. 165 

Matting by chemical means is available only for brass, copper 
and its alloys, and is effected by means of the so-called matt- 
pickle. The objects are first treated in the preliminary pickle 
mentioned above, and are then dipped in a mixture of nitric acid 
of 36 Be. 6y 2 lbs., sulphuric acid of 66° Be. 4.4 lbs., common 
salt y 2 oz., zinc sulphate j£ to J^ oz. Dissolve the zinc sul- 
phate in 3^ ozs. of water and add the solution to the cold 
mixture of the acids and the salt. The greater the quantity of 
zinc sulphate used, the more matt the articles treated with this 
matt-dipping bath will be. 

According to the degree of matt desired the articles are for 
a shorter or longer time allowed to remain in the cold matt- 
dipping bath. By heating the bath the matting action is 
accelerated. When taken from the bath, the articles are 
several times thoroughly washed in water. As the articles 
come from the matt-dipping bath with a faded, earthy appear- 
ance, they are plunged momentarily into a bright dipping-bath 
and then quickly rinsed in a large volume of water. The 
articles must not be allowed to remain too long in the bright- 
dipping bath, otherwise the matt disappears entirely. 

Lead vessels are frequently used for matt-dipping. To heat 
them they are placed in hot water. 

For the production of a matt-grained surface by pickling, 
the following mixture may be recommended : Saturated solu- 
tion of potassium dichromate 1 part by volume, and concen- 
trated hydrochloric acid 2 parts by volume. In this mixture 
the brass articles are allowed to remain several hours. They 
are then rapidly drawn through the bright-dipping bath and 
rinsed in a large volume of water frequently renewed. 

A delicate matted surface may be produced by electrolytic 
pickling or etching. The process is the same as described 
above under iron. 

Matting by mechanical means. The most simple method of 
matting is by means of brass or steel wire brushes. The wires 
of the brushes must, of course, be harder than the metal to be 
matted, and hence, for brass, copper, tombac, German silver, 



1 66 ELECTRO-DEPOSITION OF METALS. 

silver, etc., steel wire brushes will have to be employed, and 
for Britannia, gold and zinc, brass wire brushes. A swing 
brush for matting, with four knots of medium brass or steel 
wire, is shown in Fig. 78, p. 134. 

The character of the matt produced depends on the thick- 
ness of the wire of the brushes. Thicker wire gives a matt of 
a coarser grain, and thinner wire one of a finer grain. 

In larger establishments matting is frequently effected by the 
sand blast. Machines for this purpose will be described later 
on. The coarser the sand the coarser the grain of the matt 
will be. 

Matting by galvanoplasty. This is effected by providing the 
articles, previously thoroughly cleansed, with a galvanoplastic 
deposit, employing a weak current for the purpose. 

The solution used consists of water 1 quart, blue vitriol 5^ 
ozs., sulphuric acid 1 oz. The electro-motive force required 
for this bath is 0.75 to 1 volt. 

If articles of zinc, Britannia, etc., are to be matted in this 
manner, they must previously be coppered in a bath contain- 
ing potassium cyanide (see under Coppering), and the soft 
matt which is only obtained in the acid copper bath, is then 
produced by suspending the articles in the above-mentioned 
solution. 

The matt produced by galvanoplasty is very effective, and 
this method is largely employed for matt gilding uniform but- 
tons, handles of walking sticks and umbrellas, etc. 

Very beautiful effects are produced by covering with lacquer 
the portions of a lustrous surface which are to retain their 
lustre and matting the other portions in the manner above 
described. The covering layer is then removed and the entire 
article nickeled, silvered or gilded. 

Generally speaking, it may be said that less depends on the 
composition of the pickle than on quick and skillful manipula- 
tion ; and as good results have always been obtained with the 
above-mentioned mixture, there is no reason for repeating the 
innumerable receipts given for pickles. The main points are to 



TREATMENT OF METALLIC ARTICLES. 1 67 

have the acid mixture as free from water as possible, further to 
develop hyponitric acid, which is effected by the reduction of 
nitric acid in consequence of the addition of organic substances 
(lampblack, sawdust, etc.), and of chlorine, which is formed by 
the action of the sulphuric acid upon the common salt. The 
volume of the dipping bath should not be too small, since in 
pickling the acid mixture becomes heated and the increased 
temperature shows a very rapid, frequently not controllable, 
action, so that a corrosion of small articles may readily take 
place. It is therefore necessary to allow the acid mixture, 
after its preparation, to thoroughly cool off. Pour the sulphuric 
acid into the nitric acid {never the reverse/), and allow the 
mixture, which thereby becomes strongly heated, to cool off to 
at least the ordinary temperature. 

In order to be sure of the uniform action of the pickle upon 
all parts, it is, in all cases, advisable previous to pickling to free 
the articles from grease by one of the methods given later on. 

In pickling abundant vapors are evolved which have an in- 
jurious effect upon the health of the workmen, and corrode 
metallic articles exposed to them. The operation should, 
therefore, be conducted in the open air, or under a well- 
drawing vapor flue. 

In large establishments it may happen that the quantity of 
escaping acid vapors is so large as to become a nuisance to the 
neighborhood, which the proprietors may be ordered by the 
authorities to abate. The evil is best remedied by a small ab- 
sorbing plant, as follows: — 

Connect the highest point of the vapor-flue D (Fig. i<y> ) by 
a wide clay pipe R with a brick reservoir, A, laid in cement, so 
that R enters A a few centimeters above the level of the fluid, 
kept constantly at the same height by the discharge pipe b. 
Above, the reservoir is closed by a vault through which the 
water conduit W is introduced. Below the sieve S, which is 
made of wood and coated with lacquer, a wide clay pipe R x 
leads to the chimney of the steam boiler; or the suction pipe of 
an injector is introduced in this place, into which the air from 



68 



ELECTRO-DEPOSITION OF METALS. 



the vapor-flue is sucked through the reservoir and allowed to 
escape into the open air or into a chimney. Through the man- 
hole M y the sieve-bottom 5 of the reservoir is filled with large 
pieces of chalk or limestone. The manner or operating is now 
as follows : A thin jet of water falls upon 5, where it is dis- 
tributed and runs over the layer of chalk. The air of the pick- 
ling room saturated with acid vapor moves upward in conse- 
quence of the draught of the chimney of the steam boiler, the 
injector or the ventilator, and yields its content of acid to the 
layer of chalk, while the neutral solution of calcium nitrate and 
calcium chloride, which is thus formed, runs off through b. 



Fig. io6. 




«=^» 



The absorption of the acid vapors may, of course, be effected 
by apparatus of different construction, but the one above de- 
scribed may be recommended as being simple, cheap, and 
effective. 

The considerable consumption of acid for pickling purposes 
in large establishments makes it desirable to regain the acid 
and metal contained in the exhausted dipping baths. The 
following process has proved very successful for this purpose : 



TREATMENT OF METALLIC ARTICLES. 1 69 

Mix the old dipping baths with J^ their volume of concentrated 
sulphuric acid, and bring the mixture into a nitric acid distill- 
ing apparatus. Distil the nitric acid off at a moderate temper- 
ature, condense it in cooled clay-coils, and collect it in glass 
balloons. To the residue in the still add water, precipitate 
from the blue solution, which contains sulphate of copper and 
zinc, the copper with zinc waste, and add zinc until evolution 
of hydrogen no longer takes place. Filter off the precipitated 
copper through a linen bag, wash, and dry. The fluid running 
off, which contains zinc sulphate, is evaporated to crystalliza- 
tion and yields quite pure zinc sulphate, which may be sold to 
dye-works, or for the manufacture of zinc-white. 

According to local conditions, for instance, if the zinc sul- 
phate cannot be profitably sold in the neighborhood, or zinc 
waste cannot be obtained, it may be more advantageous to omit 
the regaining of zinc from the dipping baths. In this case, the 
fluid which is obtained by mixing the contents of the still with 
water is compounded with milk of lime until it shows a slightly 
acid reaction. The gypsum formed is allowed to settle, and 
after bringing the supernatant clear fluid into another reservoir, 
the copper is precipitated by the introduction of old iron. The 
first rinsing waters in which the pickled objects are washed are 
treated in the same manner. The precipitated copper is 
washed and dried. 

Removal of grease and cleansing. These two operations 
must be executed with most painstaking exactness because on 
them chiefly depends the success of the electro-plating process. 
Their object is to remove every trace of impurity, be it due to 
the touching with the hands, or to the manipulations in grind- 
ing and polishing, and to get rid of the layer of oxide which is 
formed in removing the grease with lyes and other agents. 

According to the preparatory treatment of the articles the 
removal of grease is a more or less complicated operation. 
Large quantities of oily or greasy matter should be removed 
by washing with benzine or petroleum, it being advisable to 
execute this operation immediately after grinding and polish 



I70 ELECTRO-DEPOSITION OF METALS. 

ing, so that the oil used in these operations has no chance of 
hardening, as is frequently the case with articles preparatively 
polished with Vienna lime and stearine oil. Instead of clean- 
ing with benzine or petroleum, the articles, as far as their 
nature allows, may be boiled in a hot lye consisting of 1 part of 
caustic potash or soda in 10 of water, until all the grease is 
saponified, when the dirt consisting of grinding powder, can be 
readily removed by brushing. In place of solution of caustic 
alkalies, hot solution of soda or potash may be used, but its 
action is much slower and offers no advantages. Objects of 
tin, lead and Britannia must be left in contact with the lye for 
a short time only, as otherwise they are attacked by it. 

The articles thus freed from the larger portion of grease are 
first rinsed in water, and then, for the removal of the last traces 
of grease, are brushed with a bristle brush and a mixture of 
water, quick-lime and whiting until, when rinsed in water, all 
portions appear equally moistened and no dry spots are 
visible. 

The lime mixture or paste is prepared by slaking freshly- 
burnt lime, free from sand, with water to an impalpable 
powder, mixing 1 part of this with 1 part of fine whiting, and 
adding water, stirring constantly, until a paste of the consist- 
ency of syrup is formed. 

The shape of many objects presents certain difficulties in 
the removal of grease, as the deeper portions cannot be reached 
with the brush, as, for instance, in skates, which often are to 
be nickeled in a finished state. In this case the objects are 
drawn in succession through three different benzine vessels. 
In the first benzine most of the grease is dissolved, the rest in 
the second, while the third serves for rinsing off. When the 
benzine in the first vessel contains too much grease, it is 
emptied and filled with fresh benzine, and then serves as the 
third vessel, while that which was formerly the second becomes 
the first, and the third the second. After rinsing in the third 
benzine vessel, the objects are plunged in hot water, then for a 
few seconds dipped in thin milk of lime, and finally thoroughly 



TREATMENT OF METALLIC ARTICLES. 



171 



rinsed in water. It is recommended not to omit the treatment 
with milk of lime of objects freed from grease with benzine. 

To avoid subsequent touching with the hands the objects, 
before freeing them from grease, must of course be tied to the 
metallic wires (of soft copper) by which they are suspended 
in the electro-plating bath. In removing the grease by the 
wet method a layer of oxide scarcely perceptible to the eye is 
frequently formed upon the metals. This layer of oxide has to 
be removed, the liquid used for the purpose varying, of course, 
with the nature of the layer. 

Objects of iron and steel as well as of zinc are momentarily 
plunged in a mixture of sulphuric acid 1 part by weight and 

Fig. 107. 




water 20 parts, and quickly rinsed off in clean water. Highly 
polished objects of iron and steel, after being treated with this 
mixture, are best again rapidly brushed with lime paste, and, 
after rinsing off quickly, immediately brought into the electro- 
plating bath. 

Copper, brass, bronze, German silver, and tombac are best 
cleaned with a dilute solution of potassium cyanide, 1 part of 
60 per cent, potassium cyanide in 15 to 20 of water. The 
objects are then quickly rinsed off and placed in the electro- 
plating bath. 

Lead and Britannia may be treated with water slightly 
acidulated with nitric acid. 



172 ELECTRO-DEPOSITION OF METALS. 

The steel spring carboy rocker shown in Fig. 107 overcomes 
the difficult and dangerous operation of tilting heavy carboys 
containing acids. It is the acme of convenience and simplicity. 
It empties the carboy with ease, saves waste of contents and 
time in handling, and prevents danger to the person and cloth- 
ing of the operator. It is very strong, and can be hung up out 
of the way when not in use. 



CHAPTER VI. 

PROCESSES OF ELECTRO-DEPOSITION. 

NEXT to the proper mechanical and chemical preparations of 
the objects, the success of the process of electro- deposition de- 
pends on the suitable composition of the baths, and the cur- 
rent-strength which is conducted into the baths for the preci- 
pitation of the metals. In regard to the latter the most 
essential conditions have already been discussed in Chap. IV., 
4< Electro-plating Plants in General," and will be further referred 
to in speaking of the several electro-plating processes. Hence, 
the general rules which have to be observed in the preparation 
of the baths will first be considered. 

Water being the solvent used in the preparation of all baths, 
its constitution is by no means of such slight importance as is 
frequently supposed. 

Spring and well water often contain considerable quantities 
of lime, magnesia, common salt, iron, etc., the presence of which 
may cause various kinds of separations in the baths. On the 
other hand, river water is frequently impregnated to such an 
extent with organic substances that its employment without 
previous purification cannot be recommended. No doubt, dis- 
tilled water, or in want of that rain water, is the most suitable 
for the preparation of baths. However, rain water collected 
from metal roofs should not be used, nor that running off from 
other roofs, it being contaminated with dust. When used, it 
should be caught in vessels of glass, earthenware, or wood, free 
from tannin, and filtered. Where river or well water has to be 
employed, thorough boiling and filtering before use are abso- 
lutely necessary in order to separate the carbonates of the 
alkaline earths held in solution. By boiling, a possible con- 
tent of sulphuretted hydrogen is also driven off. 

(173) 



174 ELECTRO-DEPOSITION OF METALS. 

Another important factor is the purity of the chemicals used 
for the baths, the premature failure of the latter being in most 
cases caused by the unsuitable nature of the chemicals, which 
also frequently gives rise to abnormal phenomena inexplicable 
to the operator. Chloride of zinc, for instance, may serve as 
an example. It is found in commerce in very varying quali- 
ties, it being prepared for dyeing purposes with about 70 per 
cent, actual content of chloride of zinc, for pharmaceutical pur 
poses with about 90 per cent., and for electro-plating purposes 
with 98 or 99 per cent. Now it will readily be seen that if an 
operator who is preparing a brass bath according to a formula 
which calls for pure chloride of zinc uses a preparation in- 
tended for dyeing purposes, there will be a deficiency of 
metallic zinc in the bath, and the content of copper in the 
bath being too large in proportion to the zinc present, will 
cause reddish shades in the deposits. 

Likewise, in case the operator uses potassium cyanide of 
low content, when the formula calls for a pure article with 98 
per cent., he will not be able to effect the solution of copper 
or zinc salts with the quantity prescribed. Furthermore, 
potassium cyanide, in the preparation of which prussiate of 
potash containing potassium sulphate is used, will cause, by 
reason of the formation of potassium sulpho-cyanide, various 
disturbing influences (formation of bubbles in the deposit), 
the explanation of which is difficult to the operator, who, 
trusting to the purity of the chemicals, seeks elsewhere for the 
causes of the abnormal phenomena. 

Sodium sulphate may in a similar manner cause great annoy- 
ance if the suitable preparation is not used. There is a crystal- 
lized neutral salt which is employed for many gold-baths, and 
also the sodium bisulphite in the form of powder which serves 
for the preparation of copper and brass baths. If the latter 
should be used in the preparation of gold baths, the gold 
would be reduced from the solution of its salts and precipitated 
as a brown powder. 

Or, if in preparing nickel baths a salt containing copper is 



PROCESSES OF ELECTRO-DEPOSITION. 1 75 

used, the nickeling will never be of a pure white color, but 
show shades having not even a distant resemblance to the color 
of nickel. 

The above mentioned examples will suffice to show how 
careful the operator must be in the selection of the sources 
from which he obtains his supplies. It may here be mentioned 
that all the directions given in the following pages refer to 
chemically pure products ; where products of a lower standard 
may be used their strength is especially given. 

For the concentration of the various baths, no general rules 
can be laid down; neither can the determination of the density 
of the baths by the hydrometer be relied on. If electro-plat- 
ing solutions consisted of nothing but the pure metallic salts, 
the specific gravity, which is indicated by the hydrometer- 
degrees, might serve for an estimation of their value. But such 
an estimation is often apt to prove deceptive, since, to decrease 
the resistance, the baths also require conducting salts, and by 
the addition of a larger quantity of them the specific gravity of 
a bath may be increased to any extent without the content of 
the more valuable metal being greater than in a bath showing 
fewer hydrometer-degrees. 

When the operator is acquainted with the composition of the 
baths, and knows how many degrees Be. a fresh bath should 
show when correctly prepared, he can draw a conclusion as to 
the condition of the bath by changes in the specific gravity. 
If, for instance, a nickel bath when freshly prepared shows the 
standard specific gravity — 70 Be. — for nickel baths, and it 
shows later on 90 Be., the greater specific gravity is due either 
to evaporation of water or to excessive refreshing or strengthen- 
ing of the bath. Such a bath generally yields dark or spotted 
nickeling, the deposit is formed in a sluggish manner, and 
readily scales off with a stronger current. The operator in 
this case may recognize from the hydrometer, that the cause of 
these phenomena is not due to a contamination of the bath, but 
to its over-concentration. Baths, when too concentrated, 
readily deposit salts in crystals on the anodes and the sides of 



176 ELECTRO-DEPOSITION OF METALS. 

the vats, which should by no means take place, and there is 
even danger of microscopic crystals depositing upon the 
articles and causing holes in the deposit. 

A plating bath should never be poor in metal, as otherwise 
it soon becomes exhausted, and besides the deposits form more 
slowly and with less density than in baths with a correct con- 
tent of metal. 

Hence in summer when the temperature of the baths is nat- 
urally higher, they can be made more concentrated than in 
winter. If crystals are separated, even when a bath shows a 
temperature of 58 F., they should be removed and dissolved 
in hot water. The solution is returned to the bath and water 
is added to the latter until the formation of crystals ceases. 

In order that all strata of the bath may show an equal con- 
tent of metal, it is advisable in the evening, after the day's work 
is done, to thoroughly stir up the solution with a wooden 
crutch. For practical reasons the baths are generally made 
one-quarter to one-third deeper than corresponds to the lengths 
of the objects to be plated. In consequence of this, the strata 
of fluid between the anodes and the objects become poorer in 
metal than those on the bottom, and the object of stirring up 
is to restore the same concentration to all portions of the bath. 

While stirring up the bath, it is also advisable to see whether 
any metallic articles have become detached from the slings and 
dropped to the bottom of the vat. Such articles must be taken 
out, since they are dissolved by some baths, the latter being 
thereby spoiled. This examination must be especially thor- 
ough with nickel baths. 

The strata of fluid which come in contact with the anodes 
become, by the absorption of metal, specifically heavier than 
the other strata and sink to the bottom of the vat, while, on 
the other hand, the strata of fluid which yield metal to the 
articles become specifically lighter and rise to the top. A 
partial compensation, of course, takes place by diffusion, but 
not a complete one, and from this cause arise several annoy- 
ances. The heavier and more saturated fluid offering greater 




PROCESSES OF ELECTRO- DEPOSITION. I 77 

resistance to the current, the anodes are attacked chiefly on 
the upper portions where the specifically lighter 
layer of fluid is; practically this is proved by the 
appearance of the anodes, which, at first square, 
after being for some time used assume the shape 
shown in Fig. 108. 

On the other hand, the portions of the cathodes 
(objects) which come in contact, near the surface, 
with strata of fluid poorer in metal, acquire a de- 
posit of less thickness than the lower portions which 
dip into the bath where it is richer in metal. Now, 
if the bath also contains free acid, and if there is a considerable 
difference in the specific gravity of the lower and upper strata 
of fluid, the electrode, which touches both strata, produces a 
current, the effect of which is that metal dissolves from the 
upper portions and deposits upon the lower. This explains 
the phenomenon that a deposit on the upper portions of the 
objects may be redissolved, even when a current, which, how- 
ever, must be very weak, is conducted into the bath from an 
external source. 

Many authors, therefore, go so far as to demand that during 
the electro-plating process the baths should be kept in con- 
stant agitation by mechanical means. This, however, is 
scarcely necessary, because a homogeneity of the solution is 
to a certain extent effected by the agitation of the fluid in 
suspending and taking out the objects. Hence as long as 
objects are put in and taken out an agitation naturally takes 
place in which all the strata of fluid between the objects and 
anodes take part, while only the deepest strata, which do not 
come into contact with the objects and the anodes, remain in a 
state of stagnation. 

Constant agitation of the plating solution is of advantage in 
silvering and in galvano-plastic reproduction in the acid copper 
bath, in which the articles have to remain four to five and eight 
to ten hours. With constant agitation of the bath it is possible 
to work with a greater current-tension, whereby the deposits 
12 



178 ELECTRO-DEPOSITION OF METALS. 

are finished in a shorter time; and in silvering, the formation of 
current-streaks is, to a certain extent, avoided ; and in galvano- 
plastic reproduction, the formation of so-called blooms. In 
nickeling, with constant agitation of the bath, heavier deposits 
can, without doubt, be obtained in a shorter time and without 
premature deadening of the deposit. 

Constant agitation effects also the more rapid removal of the 
hydrogen-bubbles which form on the articles, but the same end 
is attained without complicated contrivances by the operator 
accustoming himself to strike the object-rod a slight blow with 
the finger each time he suspends an object. 

The plating apparatus described below may here be re- 
ferred to. 

Bossard mechano-electroplating tanks. These tanks are pat- 
ented devices in which the work to be plated is automatically 
drawn through the bath at a controllable rate of speed. There 
are two styles of these devices, namely, the "long tank" and 
the " circular tank!' 

The advantages claimed by the inventor from the shape and 
general construction of these devices are as follows : 

1. The work to be plated, as it is drawn through the bath, 
continuously stirs the latter, thereby keeping it in active chem- 
ical condition. The hydrogen bubbles formed on the work 
are constantly dislodged, the result being a rapid, smooth, and 
homogeneous deposit. 

2. The frictional contact derived from the bearing of the 
hooks carrying the work into the bath against the cathode bar, 
insures a keen, never failing, electric action to enter the bath. 
The contact points are always clean and sure. 

3. The movement through the bath passes the work in con- 
stantly changing positions before the anodes while undergoing 
the process of deposition. 

4. To increase the movement of the work and vary the 
nature of the motion during its travel through the bath, small 
deflecting devices are introduced at desired distances along 
and upon the cathode bars, and for special work, revolving 
hooks have been used to great advantage. 



PROCESSES OF ELECTRO-DEPOSITION. 



179 



5. The proximity of the work to the anode in the plating 
bath is well known to cause conditions favorable or unfavorable 
to the formation of a good deposit. Experiments have plainly 

Fig. 109. 




APPARATUS AT WORK. 



shown, and the daily application of these devices proves, that 
the distance between the work and the anode can be consider 



i8o 



ELECTRO-DEPOSITION OF METALS. 



ably reduced and the intensity of the current increased without 
danger of burning the work when the latter is gently moved. 
By reducing distance between anode and cathode, the resist- 
ance upon the dynamo is accordingly diminished, and this 
condition is very desirable in nickel and other solutions which 
are of a neutral and non-conducting nature. 

The Bossard tanks are quite expensive and not largely used. 

Fig. 109 shows the electrolytic plating apparatus for me- 
chanical electro-plating patented by the Electrolytic Plating 
Apparatus Co., of Walsall and Birmingham, England. 

This apparatus consists of a revolving barrel immersed in 
the plating solution. As the deposit takes place it is burnished 
down, giving the same protection that burnishing silver does, 
and dispenses with previous copper plating. 



Fig. 1 10. 



Fig. 




The machine here illustrated has been adopted by the 
largest manufacturers of metal goods in Great Britain, Ger- 
many, and France. It is believed that a large proportion of 
metal goods plated in the ordinary way can be done with this 
new process, the work coming out brightly polished, saving 
wiring, buffing, and the cost of materials, enabling a vast 
quantity of articles to be plated that, owing to the cost of 
handling, could not be done before. 

The Hanson & Van Winkle Co. of Newark, N. J., have the 
sole agency for the United States and Canada of this apparatus. 

The degree of temperature required for the electro-plating 
solutions has already been discussed on page 94, where also 
the means have been given by which too cool solutions may 
be brought to the proper degree of temperature. Baths which 



PROCESSES OF ELECTRO-DEPOSITION. l8l 

are to be used cold should under no circumstances show a 
temperature below 59 F., it being best to maintain them at 
between 64.5 and 68° F. 

Boiling is required in the preparation of many baths, if, 
after cooling, they are to yield good and certain results. The 
kettles and boiling-pans used for the purpose are of various 
shapes, hemispherical or with flat bottom, and are made of 
different materials ^Figs. no and in), those of enameled 
iron, or, for small baths, of porcelain or earthenware, being 
best. The enamel of the iron kettles must be of a composi- 
tion which is not attacked by the bath. Notwithstanding their 
enamel these vessels become gradually impregnated with the 
solutions they have held, and it is dangerous to employ them 
for different kinds of baths. Thus, an enameled kettle which 
has been used for silvering will not be suitable, even after the 
most thorough washing, for a gold bath, as the gilding will 
certainly be white or green, according to the quantity of silver 
retained by the vessel. The use of metal vessels should be 
avoided. Copper and brass baths may, however, be boiled in 
strong copper kettles, though they are somewhat attacked. 
A copper kettle, after being freed from grease and scoured 
bright, may be provided with a thick deposit of nickel, by fill- 
ing it with a nickel bath, connecting it with the negative pole 
of a strong battery or dynamo machine, and suspending in it a 
number of nickel anodes connected with the positive pole. 
Such nickeled kettle may be used for boiling nickel baths, but 
enameled kettles or large dishes of nickel-sheet, or vessels 
lined with lead, deserve the preference. Generally speaking 
nickel baths do not require actual boiling, but the nickel salts 
and certain conducting salts which constitute the baths, dis- 
solve with difficulty in cold water and hence solution is effected 
in hot water. 

When, for the preparation of nickel baths, nickel salts sol- 
uble with difficulty have to be dissolved with the assistance of 
heat and no suitable vessel is available for the purpose, solution 
may be effected as follows : Bring pure water in a bright 



182 ELECTRO-DEPOSITION OF METALS. 

copper kettle to the boiling point. Pour the hot water into a 
clean wooden bucket holding from 8 to 10 quarts and add the 
quantity of nickel salt corresponding to the quantity of water. 
Stir with a wooden crutch until solution is complete. Repeat 
the operation until all the salt required is dissolved. 

For very large baths this process would, however, require 
too much time, and it is, therefore, advisable to use a large 
round or oval wooden vat, or a vat lined with pure sheet lead. 
The contents of the vat are heated by means of a lead coil 
through which steam is introduced. 

If the prepared and boiled solutions are not entirely clear, 
they have to be filtered, which for large baths is best effected 
with bags of fine felt; and for smaller baths, especially those of 
the noble metals, with filtering paper. It is still better to 
allow the baths to clarify by standing quietly and to draw off 
the clear solution by means of a siphon. The turbid residue is 
then filtered. 

To secure lasting qualities to the bath, they must be care- 
fully protected from every possible contamination. When not 
in use for plating they should be covered to keep out dust. 
The objects before being placed in the baths should be free 
from adhering scouring material or dipping fluid, which other- 
wise might, in time, spoil the bath. The cleansing of the anode 
and object rods by means of sand-paper, or emery-paper, 
should never be done over the bath, so as to avoid the danger 
of the latter being contaminated by the oxides of the metal 
constituting the rods falling into it. When a visible layer of 
dust has collected upon the bath, it must be removed, as other- 
wise particles of dust might deposit upon the articles and pre- 
vent an intimate union of the deposit with the basis-metal. 
With large baths the removal of the layer of dust is readily 
effected by drawing a large piece of filtering or tissue paper 
over the surface, and repeating the operation with fresh sheets 
of clean paper until all the dust is removed. Small baths 
should be filtered. 

The choice of anodes is also an important factor for keeping 



PROCESSES OF ELECTRO-DEPOSITION. 1 83 

the baths in good condition, as well as for obtaining good 
results. The anodes should always consist of the metal which 
is deposited from the solution ; and the metal used for them 
must be pure and free from all admixtures. To replace as 
much as possible the metal withdrawn from the bath by the 
electro- plating process, the anodes must be soluble; and it is 
wrong if, for instance, nickel baths are charged with insoluble 
anodes of carbon; or for smaller baths, of sheet platinum, pro- 
vided the chemical composition of the bath does not in part 
demand insoluble anodes. Insoluble anodes cause a steady 
and rapid declination in the content of metal, an excessive for- 
mation of acid in the bath, and, by the detachment of particles 
of carbon, a contamination of the solution. Further particulars 
in regard to anodes will be given in discussing the separate 
baths. 

When upon a pure metallic surface another metal is electro- 
deposited, the first portion of the deposit penetrates into the 
basis-metal, thus forming an alloy. This may be readily proved 
by repeating Gore's experiments : If a thick layer of copper be 
precipitated upon a platinum sheet, and then heated to a dark 
red heat, the deposit can be entirely peeled off. By then heat- 
ing the platinum sheet with nitric acid, and thoroughly wash- 
ing with water, it appears, after drying, entirely white and pure. 
By re-heating the sheet, the surface becomes again blackened 
by cupric oxide, and by frequently repeating the same opera- 
tion a fresh film of cupric oxide will always be obtained. 

This penetration of the deposit into the basis- metal, however, 
does not merely take place during electro-plating, but also later 
on; and it may frequently be observed that, for instance, zinc 
objects only slightly coppered or brassed, after some time be- 
come again white. Since this also happens when the deposits 
are protected by a coat of lacquer against atmospheric influ- 
ences, the only explanation of the phenomenon can be that the 
deposit is absorbed by the basis metal, which is also confirmed 
by analysis. This fact must be taken into consideration if dur- 
able deposits are to be produced. 



184 ELECTRO-DEPOSITION OF METALS. 

To guarantee good performance an electro-plating bath 
must fiiilfil the following conditions: — 
r. It must possess good working capacity. 

2. It must exert a sufficient dissolving action upon the 

anode. 

3. It must reduce the metal in abundance and in a reguline 

state. 

4. It must not be chemically decomposed by the metals to 

be plated, hence not by simple immersion ; the adher- 
ence of the deposit to the basis-metal being in this case 
impaired. 

5. It must not be essentially decomposed by air and light. 

Reduction of metals without a battery {electro-deposition 
by contact). 

The reduction of metals which takes place by the contact of 
two metals in one fluid without the aid of an exterior source of 
current may here be appropriately mentioned. That an elec- 
tric current is thereby generated has been previously ex- 
plained. One metal, by coming in contact with a more 
electro-positive one, becomes electro-negative and decomposes 
the fluid. If the latter is a metallic solution, and the metal 
contained in it not more strongly electro-negative than the 
negatively excited metal, a separation of metal takes place in 
consequence of decomposition. This process is termed electro- 
deposition by contact. Generally the metals which are to be 
coated are brought in contact with a bright rod of zinc, the 
latter being a highly electro-positive metal. The zinc is 
allowed to dip in only so far as actually to secure a contact 
with the metal to be coated. 

The contact of one metal with two fluids or that of two 
metals in two fluids^ presents similar phenomena, an electric 
current with visible action manifesting itself, and in the latter 
case we have a complete element. By dipping the more 
electro-negative metal in a metallic solution whose metal is 
not more electro-negative, the metal separates from the solu- 



PROCESSES OF ELECTRO-DEPOSITION. 1 85 

tion upon the metallic strip dipping in. While by the contact 
of one metal with another in one fluid, only thin deposits can 
be produced, and by coating the electro-negative metal with 
the separated metal, the contact-current loses some of its orig- 
inal strength, by immersing two metals in two fluids, deposits 
of considerable thickness can under certain conditions be pro- 
duced, as, for instance, with the galvano-plastic cell apparatus, 
which will be discussed later on. 

A reduction of metal can also be brought about by dipping 
one metal into one fluid. This may take place in consequence 
of the simple solution of the metal dipped in, and hence the 
separation may be conceived as a simple chemical action. In 
how far electric currents manifest themselves and co-operate 
thereby is still undecided. It is only known that the electro- 
positive metals, such as zinc, tin, iron, copper, can reduce the 
electro- negative metals, such as mercury, silver, gold, etc., 
from the solutions of their salts, and that the reduction is the 
more rapid and the stronger the more electro-positive the 
metal dipped in is, and the more electro-negative the dissolved 
metal is. 

Upon this action is based coppering, silvering, gilding, etc., 
by immersion. 



CHAPTER VII. 

DEPOSITION OF NICKEL AND COBALT. 

i. Nickeling. 

ALTHOUGH nickel-plating is of comparatively recent origin, 
it shall be first described, since chiefly by reason of the devel- 
opment of the dynamo-electrical machine it has steadily grown 
in popularity and become an industry of great magnitude and 
importance. The great popularity which nickel-plating enjoys 
is due to the excellent properties of the nickel itself: The 
almost silvery whiteness of the metal, its cheapness as com- 
pared with silver, and the hardness of the electro-deposited 
metal, which give the coating great power to resist wear and 
abrasion ; its capability of taking a high polish ; the fact that 
it is not blackened by the action of sulphurous vapors which 
rapidly tarnish silver, and finally the, fact that it exhibits but 
little tendency to oxidize even in the presence of moisture. 

Properties of nickel. — Pure nickel is a lustrous, silvery white 
metal with a slight steel-gray tinge. It is hard, malleable and 
ductile. Its specific gravity varies from 8.3 ( cast nickel plates) 
to 9.3 (wrought or rolled plates). It melts at about the same 
temperature as iron, but is more fusible when combined with 
carbon. It is slightly magnetic at ordinary temperatures, but 
loses this property on heating to 68o° F. 

The metal is soluble in dilute nitric acid, concentrated nitric 
acid rendering it passive, i. e., insoluble. In hydrochloric and 
sulphuric acids it dissolves very slowly, especially when in a 
compact state. 

Certain articles, for instance hot fats, strongly attack nickel, 
while vinegar, beer, mustard, tea, and other infusions produce 
stains; hence, the nickeling of culinary utensils or the use of 

(186) 



DEPOSITION OF NICKEL AND COBALT. 1 87 

nickel-plated sheet- iron for that purpose cannot be recom- 
mended. 

The chemical equivalent of nickel is 29.5. 

Nickel baths. — The first requisite in preparing nickel baths is 
the use of absolutely pure chemicals, and in choosing the nickel 
salts to be especially careful that they are free from salts of iron, 
copper, and other metals. Furthermore, it is not indifferent 
what kind of nickel salt is used, whether nickel chloride, nickel 
sulphate, the double sulphate of nickel and ammonium, etc., but 
the choice of the salt depends chiefly on the nature of the metal 
which is to be nickeled. There are a large number of general 
directions for nickel baths, of which nickel chloride, ammonio- 
nickel chloride, nickel nitrate, etc., form the active constituents, 
and yet it would be a grave mistake to use these salts for nickel- 
ing iron, because the liberated acid, if not immediately and 
completely fixed by the anodes in dissolving, imparts to the iron 
objects a great tendency to the formation of rust. Iron objects 
nickeled in such a bath, to be sure, come out faultless, but in a 
short time, even if stored in a dry place, portions of the nickel 
layer will be observed to peel off, and by closely examining 
them it will be seen that under the deposit a layer of rust 
has formed which actually tears the nickel off. The use of 
nickel sulphates or of the salts with organic acids is, therefore, 
considered best. It might be objected that the liberated 
sulphuric acid produces in like manner a formation of rust 
upon the iron objects ; but according to long experience and 
many thorough examinations such is not the case, the ten- 
dency to the formation of rust being only imparted by the 
use of the chloride and nitrate. The use of nickel salts with or- 
ganic acids is in many cases more advantageous than that of the 
sulphates, but such salts are far more expensive, and hence 
they are less frequently employed. In many prepared nickeling 
salts they form the active constituent. The composition of the 
conducting salts requires the same deliberation as that of the 
nickeling salts. To decrease the resistance of the nickel solu- 
tions, conducting salts are added to them, which are also par- 



1 88 ELECTRO-DEPOSITION OF METALS. 

tially decomposed by the current. Like the use of nickel 
chloride in nickeling iron, an addition of ammonium chloride, 
which is much liked, cannot be recommended, though the 
subsequent easy deposition of nickel with a comparatively 
weak current invites its employment. 

For copper and its alloys, zinc, etc., the chlorine combina- 
tions may be used, but for nickeling iron they must be avoided 
as the source of future evils. The use of sodium sulphide, 
sodium nitrate, barium oxalate, ammonium nitrate, sodium sul- 
phate, and ammonia-alum as conducting salts, which has been 
recommended by various authors, is unsuitable and partly in- 
jurious. With few exceptions, which will be given later on, 
the best basis for the conducting salt, according to Bottger and 
Adams, is ammonia, especially in the form of ammonia sul- 
phate or hydrochlorate, provided the latter is not used for 
baths for nickeling iron. 

Some other additions to the nickeling bath which are claimed 
to effect a pure silver-white deposit have been recommended 
by various experts. Thus, the presence of small quantities of 
an organic acid has been proposed ; for instance, boric acid by 
Weston, benzoic acid by Powell, and citric acid or acetic acid 
by others. The presence of small quantities of a free acid 
effects without doubt the reduction of a whiter nickel than is 
the case with a neutral or alkaline solution. Hence a slightly 
acid reaction of the nickeling bath, due to the presence of citric 
acid, etc., with the exclusion of the strong acids of the metal- 
loids, can be highly recommended. The quantity of free acid, 
however, must not be too large, as this would cause the deposit 
to peel off. 

Boric acid, recommended by Weston as an addition to nickel- 
ing and all other baths, has a favorable effect upon the pure 
white reduction of the nickel, especially in nickeling rough 
castings, i. e., surfaces not ground. Weston claims that boric 
acid prevents the formation of basic nickel combinations on the 
objects, and that it makes the deposit of nickel more adherent, 
softer, and more flexible. Whether with a correct current- 



DEPOSITION OF NICKEL AND COBALT. 1 89 

strength, basic nickel salts, to which the yellowish tone of the 
nickeling is said to be due, are separated on the cathode, is not 
yet proved, and would seem more than doubtful. The action 
of the boric acid has not yet been scientifically explained, but 
numerous experiments have shown that the deposition of nickel 
from nickel solution containing boric acid is neither more ad- 
herent nor softer and more flexible than that from a solution 
containing small quantities of a free organic acid. Just the 
reverse, the deposition is harder and more brittle in the pres- 
ence of boric acid, and different results may very likely be due 
to the employment of currents of varying strength. A weak 
current always and under all conditions causes the deposition 
of a harder and more brittle nickel than a current of medium 
strength; and in order to judge the quality of the deposited 
nickel from baths of varying composition, the surface of the 
objects and of the anodes must always be the same, and cur- 
rents of equal quantity and electro-motive force be conducted 
into the bath. Weston's bath will be referred to later on. 
Powell's proposition for the use of benzoic acid need scarcely 
be taken seriously, since the results from baths containing it 
differ in no respect from those without it. 

Before giving suitable formulae for the composition of nickel 
baths, it will be necessary to discuss the means of determining 
their acidity and alkalinity. As previously mentioned, a nickel 
bath, to yield a beautiful white deposit, should contain only a 
small quantity of free acid. Too much acid prevents the firm 
adherence of the deposit, while alkaline and even neutral baths 
do not yield nickel of a pure white color, but of a somewhat 
darker tone. A bath is neutral when it contains neither free 
acid nor free alkali, which is recognized by neither blue nor red 
litmus paper* being changed by the solution. Blue litmus- 
paper is colored red by acid liquids, and red litmus-paper blue 
by alkaline fluids. By simultaneously dipping one-half of a 
strip of blue and of red litmus-paper in the solution, the re- 

* Blue and red litmus-paper must be kept, each by itself, in well-closed glass jars. 



190 ELECTRO-DEPOSITION OF METALS. 

action of the fluid can be judged from the change in color, and 
the rapidity and intensity of its appearance. If a bath which, 
like most nickel baths, is to work with only a slight reaction, 
immediately and intensely reddens blue litmus paper, a suitable 
alkali has to be added until the coloration of a fresh strip of litmus- 
paper appears more slowly and less intense. If, on the other 
hand, the test shows that red litmus- paper becomes blue, and 
that consequently the bath is alkaline, a slightly acid reaction is 
restored by the gradual addition of citric acid or another acid 
suitable to the composition of the bath. Baths made with 
boric acid form an exception, and must work with a strong 
acid reaction. 

I. The most simple nickel bath consists of a solution of 8 to 
10 parts by weight of pure nickel ammonium sulphate in ioo 
parts by weight of distilled water. If too acid, the solution is 
neutralized with spirits of sal ammoniac to a slightly acid re- 
action. The solution is prepared by boiling the salt with the 
corresponding quantity of water, using in summer 10 parts of 
nickel salt to ioo of water, but in winter only 8 parts, to pre- 
vent the nickel salt from crystallizing out. This bath, which 
is frequently used, possesses, however, a considerable degree 
of resistance to conduction, and hence requires a strong cur- 
rent for the deposition of the nickel. It also requires cast 
nickel anodes, since with the use of rolled anodes nickeling 
proceeds in a very sluggish manner. However, the cast anodes 
rapidly render the bath alkaline, necessitating a frequent cor- 
rection of the reaction. To decrease the resistance, recourse 
has been had to certain conducting salts, and, below, the more 
common nickel baths will be discussed, together with their 
mode of preparation and action, as well as their availability for 
certain purposes. 

II. Nickel ammonium sulphate 17 ozs., ammonium sulphate 
17 ozs., distilled water 10 quarts. 

Boil the salts with the water, and, if the solution is not too 
acid, restore its neutrality by spirits of sal ammoniac; then 
gradually add solution of citric acid until blue litmus-paper is 



DEPOSITION OF NICKEL AND COBALT. 191 

slowly but visibly reddened. The bath deposits rapidly, it 
possessing but little resistance. An electro-motive force of 1.8 
to 2 volts suffices, and all metals (zinc, lead, tin, and Britannia, 
after previous coppering) can be nickeled in it. However, 
upon rough castings and iron a pure white deposit is difficult 
to obtain, frequent scratch-brushing with a medium hard steel 
brush being required. On account of the great content of 
sulphate of ammonium in the bath, the nickel deposit piles up 
especially on the lower portions of the objects, which, in conse- 
quence, readily become dull {burn or over-nickel, for which see 
later on), while the upper portions are not sufficiently nickeled. 
For this reason the objects must be frequently turned in t]ie 
bath so that the lower portions come uppermost. This piling 
up of the deposit also frequently prevents the latter from 
acquiring a uniform thickness. 

III. Nickel ammonium sulphate 25^ ozs., ammonium sul- 
phate 8 ozs., crystallized citric acid 1^ ozs., water 10 to 12 
quarts. 

The bath is prepared in the same manner as the preceding, 
the salts being dissolved in boiling water, and ammonia added 
until blue litmus-paper is only slightly reddened. 

This bath requires a somewhat greater electro- motive force 
than the preceding, or about 2 to 2.2 volts. The formation of 
the deposit is, however, more uniform, the nickeling of a 
beautiful white color, dense and hard and, consequently, when 
the deposit is thick enough, it will bear a high polish without 
danger of the nickel grinding off. This bath (III.) is very 
suitable for nickeling ground surgical instruments as well as 
every kind of ground iron articles which are to receive a thick 
and solid deposit. It is also well adapted for heavy nickeling 
of copper, brass, bronze, etc. This bath with or without the 
addition of citric acic was formerly in general use in this 
country. It requires, however, careful regulation of the cur- 
rent-strength to avoid peeling off, and to overcome this ten- 
dency to peeling off, it is advisable to decrease the content of 
ammonium sulphate. The bath should show only a very 



192 ELECTRO-DEPOSITION OF METALS. 

slightly acid reaction, or should be neutral, and it is best to use 
an equal number of cast and rolled nickel anodes. 

If, after working for some time, the nickeling becomes dark, 
an addition of nickel sulphate is advisable. 

IV. Nickel ammonium sulphate 23 ozs., ammonium chloride 
(crystallized) 11^ ozs., water 10 to 12 quarts. 

The bath is prepared in the same manner as given for II. 
and III. It nickels very rapidly and quite white, but the de- 
posit is soft, and hence care must be had in polishing upon 
cloth or felt bobs, the corners and edges of the objects espec- 
ially requiring careful handling. On account of the danger of 
peeling off, a heavy deposit of nickel cannot be obtained in this 
bath, since, in consequence of the rapid precipitation, the de- 
posit condenses and absorbs hydrogen, is formed with a coarser 
structure, and turns out less uniform and dense. These phe- 
nomena are a hindrance to a heavy deposit, which, if it is to 
adhere, must be homogeneous and dense. As previously men- 
tioned, baths with the addition of chlorides as well as those pre- 
pared with nickel chloride and nickel nitrate are not suitable for 
the solid nickeling of iron. They are, however, well adapted to 
the rapid light nickeling of cheap brass articles. The electro- 
motive force required for this bath is 1.8 volts. 

V. Nickel chloride (crystallized) 17^ ozs., ammonium 
chloride (crystallized) 17% ozs., water 12 to 15 quarts. 

This bath is prepared by dissolving the salts in lukewarm 
water and adding spirit of sal ammoniac until the bath shows 
a very slightly acid, or a neutral, reaction. The bath deposits 
readily and is especially liked for nickeling zinc castings. 
Tension of current 1.5 to 1.75 volts; for zinc higher. 

VI. Baths containing boric acid. Weston recommends the 
following composition for nickel baths: Nickel chloride 17^ 
ozs., boric acid 7 ozs., water 20 quarts; or nickel-ammonium 
sulphate 35 ozs., boric acid vjyi ozs., water 25 to 30 quarts. 
Both solutions are said to be improved by adding caustic 
potash or caustic soda so long as the precipitate formed by the 
addition dissolves. 



DEPOSITION OF NICKEL AND COBALT. 1 93 

These compositions, however, cannot be recommended, be- 
cause the baths work faultlessly fur a comparatively short time 
only. All kinds of disturbing phenomena very soon make 
their appearance, the deposit being no longer white but black- 
ish, and the baths soon failing entirely. Kaselowsky's formula 
yields similar results. This bath is prepared by dissolving, 
with the assistance of heat, 35 % ozs. of nickel ammonium sul- 
phate and iy%& ozs. of boric acid in 20 quarts of water. This 
bath also generally fails after two or three months' use. The 
cause of this has to be primarily sought for in the fact that baths 
prepared with boric acid require according to their composi- 
tion a definite proportion between rolled and cast nickel anodes. 
If rolled anodes are exclusively used, free sulphuric acid is 
soon formed, which causes energetic evolution of hydrogen on 
the articles, but prevents a vigorous deposit and imparts to the 
latter a tendency to peel off. The same thing happens when 
a nickel salt not entirely neutral has been used in the prepara- 
tion of the bath. If, on the other hand, cast nickel anodes 
alone are employed, the bath soon becomes alkaline, with 
turbidity and the formation of slime, and the deposit turns out 
gray and dull before it possesses sufficient thickness. 

From the foregoing it will be readily understood that the 
nickel salt used must be neutral and that the proportion of 
rolled to cast anodes must be so chosen that the free sulphuric 
acid formed on the cast anodes is neutralized, but that the 
acidity of the bath dependent on the free boric acid is con- 
stantly maintained. 

Such a bath containing boric acid may advantageously be 
prepared as follows : 

VII. Nickel-ammonium sulphate 21 ozs., chemically pure 
nickel carbonate 1 ^ ozs., chemically pure boric acid (crys- 
tallized) 10^ ozs., water 10 to 12 quarts. 

Boil the nickel-ammonium sulphate and the nickel carbonate 

in the water until the evolution of bubbles of carbonic acid 

ceases and blue litmus-paper is no longer reddened. After 

allowing sufficient time for settling, decant the solution from 

13 



194 ELECTRO-DEPOSITION OF METALS. 

any undissolved nickel carbonate and add the boric acid. 
Boil the whole a few minutes longer, and allow to cool. If the 
nickel salt contains no free acid, boiling with the nickel car- 
bonate may be omitted. The solution shows a strongly acid 
reaction, which must not be removed by alkaline additions. 

The proportion of cast to rolled anodes used in this bath is de- 
pendent on the quality of the anodes. The use of readily sol- 
uble cast anodes requires the suspension in the bath of more 
rolled anodes than when cast anodes dissolving with difficulty 
are employed, since the surfaces of the latter, in consequence 
of rapid cooling, are not readily attacked. The proportion has 
likewise to be changed, with the use of soft or hard-rolled 
anodes. Hence the proper proportion will have to be estab- 
lished by frequently testing the reaction of the bath. For this 
purpose the following rules may be laid down: Blue litmus- 
paper must always be perceptibly and intensely reddened, but 
congo-paper should not change its red color, for if the latter 
turns blue it is an indication of the presence of free sulphuric 
acid in the bath, which has to be neutralized by the careful 
addition of solution of soda or potash until a fresh piece of 
congo-paper dipped in the bath remains red. Ammonia 
cannot be recommended for neutralizing free sulphuric acid in 
this bath. Red litmus- paper must remain red, for if it turns 
blue, the bath has become alkaline and fresh boric acid has to 
be dissolved in the previously heated bath until a fresh piece 
of blue litmus paper acquires an intense red color. 

The bath prepared according to the above formula (VII) 
requires an electro-motive force of about 2.3 to 2.5 volts. 

Below are given a few other formulae for nickel baths which 
may be advantageously used for special purposes ', but not for 
nickeling all kinds of metals with equally good results. 

VIII. Nickel sulphate \o x / 2 ozs., potassium citrate 7 ozs., 
ammonium chloride 7 ozs., water 10 to 12 quarts. 

To prepare the bath dissolve 10^ ounces of nickel sulphate 
and ^y 2 ounces of pure crystallized citric acid in the water; 
neutralize accurately with caustic potash, and then add the 



DEPOSITION OF NICKEL AND COBALT. 1 95 

ammonium chloride. This bath is especially adapted for the 
rapid nickeling of polished, slightly coppered zinc articles. 
Deposition is effected with a very feeble current, without the 
formation of black streaks, such as are otherwise apt to appear 
in nickeling with a weak current. The deposit itself is dull 
and somewhat gray, but acquires a very fine polish and pure 
white color by slight manipulation upon the polishing wheels. 
With a stronger current the bath is also suitable for the direct 
nickeling of zinc articles ; it must, however, be kept strictly 
neutral. The bath works with rolled anodes, and but seldom 
requires a correction of the reaction. 

IX. Nickel phosphate S}4 ozs., sodium pyrophosphate 26*^ 
ozs., water 10 to 15 quarts. Dissolve the sodium pyrophos- 
phate in the water, heat the solution to about 167 F. and add 
the nickel phosphate with constant stirring. Nickel phosphate 
is obtained as a pale green powder by precipitating solution of 
nickel sulphate with sodium phosphate. 

This bath yields a very fine dark nickeling upon iron, brass, 
and copper, as well as directly, without previous coppering, 
upon sheet zinc and zinc castings, and may be advantageously 
used for decorative purposes where darker tones of nickel are 
demanded. 

For nickeling of a dark tone, Pfanhauser recommends a bath 
quite poor in nickel, showing an ammoniacal or alkaline re- 
action. A weak current should be employed and very small 
rolled nickel anodes. He gives the following solutions as suit- 
able for the purpose : Water 1 quart, nickel-ammonium sul- 
phate 0.35 oz., spirits of sal ammoniac 1^ ozs.; or: Water 1 
quart, nickel-ammonium sulphate 0.35 oz., sodium hyposul- 
phate 1 y^ ozs., spirits of sal ammoniac 1 ^ ozs. 

X. A fairly good nickel-bath for electro-platers having but a 
feeble current at their disposal is obtained from a solution of 
nickel-ammonium sulphate 22^ ozs., magnesium sulphate 
nj^ ozs., water 10 to 12 quarts. 

This bath precipitates readily and strongly, and a heavy 
coating can also be deposited upon iron without fear of the 



I96 ELECTRO-DEPOSITION OF METALS. 

disagreeable consequences of bath IV. Even zinc may be 
directly nickeled in it with a comparatively feeble current. 
The deposit, however, turns out rather soft, with a yellowish 
tinge, and the bath does not remain constant, but fails after 
working at the utmost three or four months, the anodes being 
scarcely attacked. 

Below are given the compositions of a few nickel baths which 
have been highly recommended : — 

XI. Pure nickel sulphate 35 ]/ 2 ozs., neutral ammonium tar- 
trate 26^ ozs., tannin 77 grains, water 20 quarts. Neutral 
ammonium tartrate is obtained by saturating a solution of tar- 
taric acid with ammonia. The nickel salt must also be neutral. 
For this purpose dissolve the above-mentioned ingredients in 3 
or 4 quarts of water and boil the solution for y£ hour, then add 
enough water to make 20 quarts of fluid, and filter. The bath 
is said to yield a very white, soft, and homogeneous deposit of 
any desired thickness, without roughness or danger of peeling 
off. On rough or polished castings thick deposits may be ob- 
tained at a cost scarceiy exceeding that of coppering. Gal- 
vano-plastic reproduction may also be effected in this bath. 
For those who wish to try the bath it may be mentioned that 
the most suitable current-strength is 3.5 volts. 

XII. An English formula is as follows: Dissolve 17^ ozs. 
of nickel sulphate, g 1 /^ ozs. of tartaric acid, and 2^ ozs. of 
caustic potash in 10 quarts of water. 

The addition of bisulphide of carbon to nickel baths, which 
has been recommended by Bruce, is not advisable. Accord- 
ing to Bruce, such an addition prevents the nickel deposit 
from becoming dull when reaching a certain thickness, but re- 
peated experiments made strictly in accordance with the direc- 
tions given did not confirm this statement. 

XIII. For nickeling small articles the following bath is 
claimed to yield excellent results : Nickel-ammonium sulphate 
64 ozs., ammonium sulphate 20^ ozs., crystallized citric acid 
4^ ozs. 

For the production of very thick deposits, the following bath 



DEPOSITION OF NICKEL AND COBALT. 1 97 

has been recommended: Nickel sulphate 16 ozs., sodium 
citrate 10 ozs., water 10 quarts. This bath is said to be 
especially useful in preparing nickel cliches. However, numer- 
ous experiments proved it to possess the disadvantages of all 
nickel baths prepared with large quantities of organic com- 
binations, and for the special purpose for which it is recom- 
mended no better results were obtained than with any other 
nickel bath rationally composed for heavy deposits. 

Some authors have recommended for nickeling a solution of 
nickel cyanide in potassium cyanide, but experiments failed to 
obtain a proper deposition of nickel. 

The general remark may here be added that freshly prepared 
nickel baths mostly work correctly from the start, though it 
may sometimes happen that the articles first nickeled come 
from the bath with a somewhat darker tone. In such case it 
is advisable to suspend a few anodes to the cathode and allow 
the bath to work one or two hours, when nickeling will proceed 
faultlessly. If, however, such should not be the case, test the 
specific gravity of the bath with the hydrometer. The stand- 
ard specific gravity is 6° to 7 Be., and if the bath shows a 
greater specific gravity dilute it to 7 Be. If after dilution the 
deposit is not of a light color, the nickel salt very likely con- 
tains traces of copper. 

It has further been observed that freshly prepared baths de- 
posit a somewhat more brittle nickel, and that the deposit 
shows a tendency towards peeling off. The cause of this phe- 
nomenon is not thoroughly understood, but perhaps it is due 
to an increased occlusion of hydrogen. When this phe- 
nomenon is observed it is advisable very carefully to free the 
articles from grease and clean them, and during the first days 
not to force the thickness of nickeling too far. If peeling off 
is nevertheless observed, even when the reactions of the bath 
are correct, allow the bath to work for some time in the man- 
ner described above. Older baths yield very flexible deposits 
and are less sensitive towards an incorrect current. 

It may also be mentioned that peeling off is frequently 



I9« ELECTRO-DEPOSITION OF METALS. 

observed when additions for the purpose of neutralization have 
been made to nickel baths. This phenomenon disappears in a 
few days, but it demonstrates that, instead of correcting the 
reaction of the bath by the addition of acids or alkalies, it 
should be done by increasing the rolled anodes in case the 
bath has a tendency to become alkaline, or to increase the cast 
anodes in case the bath becomes too acid. 

A few words may here be said in regard to what may be 
termed a nickel bath without nickel salt. It simply consists of 
a 15 to 20 per cent, solution of ammonium chloride, which 
transfers the nickel from the anodes to the articles. Cast 
anodes are almost exclusively used for the purpose, and deposi- 
tion may be effected with quite a feeble current. Before the 
solution acquires the capacity of depositing, quite a strong cur- 
rent has to be conducted through the bath until the commence- 
ment of a proper reduction of nickel. This bath is only suit- 
able for coloring very cheap articles, it not being possible to 
produce solid nickeling with it. It is here mentioned because 
it may serve as a representative of a series of other electro- 
plating baths in which the transfer of the metal is effected by 
sal ammoniac solution without the use of metallic salts, for 
instance, iron, zinc, cobalt, etc. 

The heating of nickel baths, which is in favor with some 
platers, may here be referred to. In a heated bath the deposit 
forms more rapidly in consequence of the slighter resistance, 
and because less current-tension is required. However, by 
reason of general complaints that deposits effected in a heated 
bath peel off, the use of such a bath for nickeling would not 
appear advisable. 

Nickel anodes. — Either cast or rolled nickel plates are used as 
anodes, which must of course be as pure as it is possible to ob- 
tain them. Every impurity of the anodes passes into the bath 
and jeopardizes its successful working. If too thin the anodes 
increase the resistance. For small baths rolled anodes 0.079 
inch thick are generally used, and as a rule they should not be 
less than 0.039 inch thick. For larger baths it is better to use 



DEPOSITION OF NICKEL AND COBALT. 1 99 

plates from 0.11 to 0.19 inch thick, while the thickness of cast 
anodes may vary between 0.11 and 0.39 inch, according to the 
size of the bath and the purpose for which it is to be used. 
The use of insoluble anodes of gas-carbon or platinum, either 
by themselves or in conjunction with nickel anodes, as fre- 
quently recommended, is not advisable. The harder and the 
less porous the nickel anode is, the less it is attacked in the 
bath and the less it fulfils the object of keeping constant the 
metallic content of the solution. On the other hand, the softer 
and the more porous the anode is, the more readily it dissolves, 
because it conducts the current better and presents more points 
of attack to the bath ; and the more it is dissolved, the mure 
metal is conveyed to the bath. With the sole use of rolled 
anodes and working with a feeble current, free acid is formed 
in the bath ; on the other hand, by working with cast anodes 
alone, the bath readily becomes alkaline. Now it would appear 
that the possibility of a bath also becoming alkaline even with 
the sole use of rolled anodes, especially when working with a 
strong current, has led to the proposal of suspending in the 
bath, besides the nickel anodes, a sufficient number of insoluble 
anodes in order to effect a constant neutrality of the bath. It 
would lead too far to go into the theory of the secondary de- 
compositions which take place in a nickel bath, to prove that, 
though neutrality is obtained, it can only be done at the expense 
of the metallic content of the bath. Hence, this impracticable 
proposal shall here be overthrown by practical reasons, it only 
requiring to be demonstrated that in baths becoming alkaline 
the content of nickel also decreases steadily though slowly. 
This fact in itself shows that in order to save the occasional 
slight labor of neutralizing the bath, the decrease of the me- 
tallic content should not be accelerated by the use of insoluble 
anodes. For larger baths the use of expensive platinum 
anodes as insoluble anodes need not be taken into considera- 
tion, because for large surfaces of objects correspondingly 
large surfaces of platinum anodes would have to be present, as 
otherwise the resistance of thin platinum sheets would be con- 



200 ELECTRO-DEPOSITION OF METALS. 

siderable. But such an expensive arrangement would be justi- 
fiable only if actual advantages were obtained, which is not the 
case, because, though the platinum does absolutely not dis- 
solve, the deficiency of metallic nickel in the bath caused by 
such anodes must in some manner be replaced. The insoluble 
anodes of gas-carbon, which have frequently been proposed, are 
attacked by the bath. Particles of carbon become constantly 
detached, and floating upon the bath, deposit themselves upon 
the objects and cause the layer of nickel to peel off. Further- 
more, by the use of nickel anodes in conjunction with carbon 
anodes, the current, on account of the greater resistance of the 
latter, is forced to preferably take its course through the me- 
tallic anodes, in consequence of which the articles opposite the 
nickel anodes are more thickly nickeled than those under the 
influence of the carbon anodes. With larger objects this in- 
equality in the thickness of the deposit is again a hindrance to 
obtaining layers of good and uniform thickness, such as are 
required for solid nickeling. Since the current preferably 
seeks its compensation through these separate metallic anodes, 
they are more vigorously attacked than when nickel plates 
only are suspended in the bath. 

With nickel baths which contain a considerable amount of 
ammonium chloride, the use of a few carbon anodes along with 
the rolled nickel anodes may be permissible, since these baths 
strongly attack evert the rolled anodes, and thereby convey to 
the bath sufficient quantities of fresh nickel. Such baths con- 
taining ammonium chloride, as a rule, become very rapidly 
alkaline, so that frequent neutralization becomes inconvenient. 
However, in this case, it is advisable to place the carbon anodes 
in small linen bags which retain any particles of carbon becom- 
ing detached, the latter being thus prevented from depositing 
upon the articles in the bath. 

According to long practical experience, the best plan is to 
use rolled and cast anodes together in a bath. The proportion 
of cast to rolled anodes depends on the composition of the 
bath, but it may be laid down as a rule, that baths with greater 



DEPOSITION OF NICKEL AND COBALT. 201 

resistance require more cast anodes, and baths with less resist- 
ance more rolled anodes. The proper proportion has been 
established when, after working for some time, the original re- 
action of the bath remains as constant as possible. When the 
bath is observed to become alkaline the number of rolled 
anodes should be increased, but when the content of acid in- 
creases they should be decreased, and the number of cast 
anodes increased. 

Cast anodes, to be sure, have the disadvantage of becoming 
brittle, and crumbling before they are entirely consumed. 
Nickel anodes cast in iron moulds are so hard on their sur- 
faces as to resist the action of the bath, and dissolve only with 
difficulty, so that the content of metal of the bath is only in- 
completely replenished. Anodes cast in sand moulds, and 
slowly cooled, are porous and consequently dissolve readily, 
but by reason of their porosity their interior portions are 
also attacked. If such an anode be broken, it will be found 
that the interior contains a black powder (nickel oxide) which 
novices sometimes believe to be carbon. In fact cases have 
been heard of that customers have complained that the anodes 
furnished them were not nickel anodes at all, but simply car- 
bon plates coated with a layer of nickel. 

The cast anodes suspended to the ends of the conducting 
rods are especially strongly attacked, and, therefore, when 
rolled and cast anodes are used together, it is best to suspend 
the latter more towards the centre, and the former on the ends 
of the rods. 

These disadvantages, however, are not sufficient to prevent 
the use of a combination of cast and rolled anodes when re- 
quired by the composition of the bath. The brittle remnants 
are thoroughly washed in hot water, dried and sold. 

The rolled nickel anodes are less liable to corrosion, and may 
be used up to the thickness of a sheet of paper before they fall 
to pieces. It is, however, best to replace them by fresh 
anodes before they become too thin, since with the decrease in 
thickness their resistance increases. 



202 ELECTRO-DEPOSITION OE METALS. 

The surface of the anodes suspended in the baths should be 
at least as large as that of the articles to be nickeled. It is, 
however, preferable that they should present twice or three 
times the surface, so that the bath may be kept thoroughly 
saturated with nickel. 

It is best to allow the anodes to remain quietly in the bath, 
even when the latter is not in use, they being in this case not 
attacked. By frequently removing and replacing them they 
are subject to concussion, in consequence of which they 
crumble much more quickly than when remaining quietly in 
the bath. 

In the morning, before nickeling is commenced, the anodes 
will frequently show a reddish tinge, which is generally ascribed 
to a content of copper in the bath or in the anodes. This red- 
dish coloration also appears when an analysis shows the anodes 
as well as the bath to be absolutely free from copper. It is 
very likely due to a small content of cobalt, from which nickel 
anodes can never be entirely freed. It would seem that by the 
action of a feeble current cobaltous hydrate is formed, which, 
however, immediately disappears on conducting a strong cur- 
rent through the bath. 

The anodes are supported by nickel wire o.u to 0.19 inch 
thick, or by strips of nickel sheet riveted on. 

If after working for some time a nickel bath has become 
alkaline, which can be readily determined by testing with litmus- 
paper, its neutrality or a slightly acid reaction can in a few 
minutes be restored by the addition of either citric, sulphuric, 
acetic, or boric acid, according to the composition of the bath. 
On the other hand, when the bath contains too much free acid, 
it is removed by the addition of spirits of sal ammoniac, am- 
monium carbonate, potash, or by boiling with nickel carbonate, 
the choice of the remedy depending on the composition of the 
bath. 

Process of nickeling. — Next to the correct composition of the 
bath and the proper selection of the anodes, the success of the 
nickeling process depends on the articles having been carefully 



DEPOSITION OF NICKEL AND COBALT. 203 

freed from grease and cleansed, and on the correct current- 
strength. 

The directions for the removal of grease, etc., given on p. 
r69, also apply to objects to be nickeled. In executing the 
operations, it should always be borne in mind that though 
dirty, greasy parts become coated with nickel, the deposit im- 
mediately peels off by polishing, because an intimate union of 
the deposit with the basis- metal is effected with only perfectly 
clean surfaces. Touching the cleansed articles with the dry 
hand must be strictly avoided ; but, if large and heavy objects 
have to be handled, the hands should first be freed from grease 
by brushing with lime and rinsing in water, and be kept wet. 

As previously mentioned, the cleansed objects must not be 
exposed to the air, but immediately placed in the bath, or, if 
this is not practicable, be kept under clean water. 

While copper and its alloys (brass, bronze, tombac, German 
silver, etc.), as well as iron and steel, are directly nickeled, zinc, 
tin, Britannia and lead are generally first coppered or brassed. 
With a suitable composition of the nickel bath and some ex- 
perience, the last-mentioned metals may also be directly nick- 
eled ; but, as a rule, previous coppering or brassing is prefer- 
able, the certainty and beauty of the result being thereby 
considerably enhanced. 

By many operators it is preferred to copper iron and steel 
articles before nickeling, it being claimed that by so doing 
better protection against rust is secured. However, compara- 
tive experiments have shown that with the thin coat of copper 
which, as a rule, is applied, this claim is scarcely tenable, and 
the conclusion has been reached that a thick deposit of nickel 
obtained from a bath of suitable composition protects the iron 
from rust just as well and as long as if it had previously been 
slightly coppered. It cannot be denied that previous copper- 
ing of iron articles has the advantage, that in case the articles 
have not been thoroughly cleansed, the deposit of nickel is less 
liable to peel off, because the alkaline copper bath completes 
the removal of grease ; but with objects carefully cleansed ac- 



204 ELECTRO-DEPOSITION OF METALS. 

cording to the directions given on p. 169, previous coppering 
is not necessary. 

The case, however, is different if the copper deposit is pro- 
duced in order to act as a cementing agent for two nickel de- 
posits. If, for instance, parts which have previously been 
nickeled and from which the old deposit cannot be removed 
by mechanical means, are to be re-nickeled, coppering is re- 
quired, because the new deposit of nickel adheres very badly 
to the old. Where articles are to be protected as much as 
possible from rust, coppering is advisable, but the best success 
is attained by a method different from the one generally pur- 
sued. In nickeling, for instance, parts of bicycles which are 
exposed to all kinds .of atmospheric influences, they are 
first provided with a thick deposit of nickel, then with a thick 
coat of copper, and finally, again nickeled, they thus being 
twice nickeled. It has previously been mentioned that every 
deposit is formed net-like, the meshes of the net being larger 
or smaller, according to the nature of the metal deposited. If 
now thick layers of two different metals are deposited one on 
the top of the other, the net-lines of one deposit do not con- 
verge into those of the previous deposit, but are deposited be-- 
tween them, thus consolidating the net. It will now be readily 
understood that by the subsequent polishing the further con- 
solidation of the deposits will be far more complete than when 
the basis-metal receives but one deposit, which is to be con- 
solidated by polishing. It is a remarkable fact that the porosity 
of the nickel-deposit varies if the article is nickeled in several 
baths of different composition. Thus denser deposits may be 
obtained by suspending the articles in two or three baths, 
which proves that the different resistances of the respective 
baths of one and the same metal exert an influence upon the 
greater or slighter density of the net. 

The objects should never be suspended in the bath without cur- 
rent, since the baths, with few exceptions, exert a chemical action 
upon many metals which is injurious to the electro-plating 
process, and especially with nickel baths it is necessary to con- 



DEPOSITION OF NICKEL AND COBALT. 205 

nect the anode-rods and object-rods before suspending the 
articles. 

The suitable current- strength has already been fully discussed 
on p. 97 et seq. (" Electro-plating Arrangements in Particu- 
lar"), and referring the reader to that section we may here be 
comparatively brief. 

In that section it has been said that the surfaces of objects 
to be nickeled must be in due proportion to the effective zinc 
surface of the battery if the latter be used for generating the 
current; further, the surface of anodes suspended in the bath 
must be at least equal to that of the objects, though in most 
cases it is better that it should be larger. On p. 97 et seq., it 
has also been explained how, according to circumstances, the 
elements have to be coupled to a battery in order to be sure of 
success. Two Bunsen elements, coupled one after the other, 
yield for nearly all nickel baths the electro motive force re- 
quired for the reduction of the nickel. For baths with great 
resistance it will, however, be better, especially when the filling 
of the elements is no longer fresh, to couple three elements, 
one after the other, and to neutralize a momentary excess of 
current by the resistance-board. 

An error is frequently committed in nickeling with too strong 
a current, the consequence being that the deposit on the lower 
portions of the objects soon becomes dull and gray-black, 
while the upper portions are not sufficiently nickeled. This 
phenomenon, which is due to the reduction of the nickel with 
a coarse grain in consequence of too powerful a current, is 
called burning or over- nickeling. A further consequence of 
nickeling with too strong a current is that the deposit readily 
peels off after it reaches a certain thickness. The phenomenon 
is due to the hydrogen being condensed and retained by the 
deposit, which is thereby prevented from acquiring greater 
thickness. 

Especially do those objects suspended on the ends of the 
rods nickel with great ease. This evil can be avoided by hang- 
ing on both ends of the rods a strip of copper-sheet about 0.39 



206 ELECTRO-DEPOSITION OF METALS. 

inch wide, and of a length corresponding to the depth of the 
bath. 

The following criteria may serve for judging whether the 
nickeling progresses with a correct current-strength: In two or 
at the utmost three minutes all portions of the objects must be 
perceptibly coated with nickel, but without a violent evolution of 
gas on the objects. Small gas bubbles rising without violence 
and with a certain regularity are an indication of the operation 
progressing with regularity. If, after two or three minutes, 
the objects show no deposit, the current is too weak, and in 
most cases the objects will have acquired dark, discolored 
tones. In such case either a stronger current must be intro- 
duced by means of the resistance board, or, if the entire vol- 
ume of current generated already passes into the bath, the 
object-surface has to be diminished, or, if this is not desired, 
the battery must be strengthened by adding more elements, or 
by fresh filling, etc. 

If, on the other hand, a violent evolution of gas appears on 
the objects, and the latter are well covered in a few seconds, 
and the at first white and lustrous nickeling changes in a few 
minutes to a dull gray, the current is too strong, and must be 
weakened either by the resistance board, or uncoupling a few 
elements, or diminishing the anode-surface, or finally by sus- 
pending more objects in the bath. 

These criteria also apply to nickeling with the dynamo. 

The density of current most suitable for nickeling copper, 
copper-alloys, iron and steel is 0.6 ampere per 15.5 square 
inches, while zinc previously coppered requires 1.2 amperes. 

It will be seen that in nickeling zinc objects greater density 
of current and higher tension are required. If the current is 
not of sufficient strength, black streaks and stains are formed, 
zinc is dissolved and the nickel bath spoiled. These evils are 
frequently complained of by nickel-platers who have not a clear 
perception of the prevailing conditions (see polarizing current). 
A vigorous evolution of gas must take place on the zinc ob- 
jects, otherwise a serviceable deposit will not be obtained. 



DEPOSITION OF NICKEL AND COBALT. 207 

In most cases the electro-plater will in a few days learn 
correctly to judge the proper current-strength by the pheno- 
mena presented by the objects, and if he closely follows the 
directions given but few failures will result. It may here be 
again repeated that the use of a voltmeter as well as of a 
resistance board greatly facilitates a correct estimate of the 
proper current-strength, and these instruments should for the 
sake of economy never be omitted in fitting up an electro- 
plating plant. 

It is in every case advisable first to cover the objects, i. e. y to 
effect the first deposit of nickel, with the use of a strong cur- 
rent, in order to withdraw the metals from the action of the 
solution. The current is then reduced to a suitable strength 
and nickeling finished with this current. With a current thus 
regulated, the objects may be allowed to remain in the bath for 
hours and even for days. It is further possible to nickel by 
weight and attain deposits of considerable thickness. 

If very thick deposits of nickel are desired, the objects must 
be frequently turned in the bath, as the lower portions nickel 
stronger than the upper; further, as soon as the deposit ac- 
quires a dull bluish lustre it has to be thoroughly scratch- 
brushed, in doing which, however, the objects must not be 
allowed to become dry. After scratch-brushing it is advisable 
to cleanse the deposit once more with the lime-brush, and after 
rinsing replace the objects in the bath. If burnt places cannot 
be brightened and smoothed with the scratch-brush, the de- 
sired end is readily attained with the assistance of emery paper 
or pumice. 

For solid nickeling it suffices in most cases to allow the ob- 
jects to remain in the bath until a dull bluish lustre appears, 
this being an indication that the deposit has acquired consider- 
able thickness, and will not take a further regular deposit. If 
such objects are permitted to remain longer in the bath without 
scratch-brushing, the dull bluish tone soon passes into a dull 
gray, and all the metal deposited in this form must be polished 
away in order to obtain a bright lustre. 



208 ELECTRO-DEPOSITION OF METALS. 

Whether the deposit of nickel is sufficiently heavy for all 
ordinary demands is, according to Fontaine, shown by rubbing 
a nickeled corner or edge of the object rapidly and with ener- 
getic pressure upon a piece of planed soft wood until it be- 
comes hot. The nickeling should bear this friction. This test 
can be recommended as perfectly reliable. 

If the objects, after having been suspended for some time in 
the bath, are only partially nickeled, it is very likely due to the 
defective arrangement of the anodes. This occurs chiefly with 
large round objects and with articles having deep depressions 
(cups, vases, etc.). 

For flat objects it is sufficient to suspend them between two 
rows of anodes. Round objects with a large diameter should 
be quite surrounded with anodes, and be as nearly as possible 
equi-distant from them. This arrangement should especially 
not be neglected where a heavy and uniform deposit of nickel 
is to be given to round or half-round surfaces — for instance, 
large half-round stereotype plates for revolving presses. 

The arrangement of two object rods between two anode-rods 
is permissible only for small and thin articles such as safety- 
pins, crochet needles, lead-pencil holders, etc. For articles 
with larger surfaces it is decidely objectionable, because the 
sides of the articles turned towards the anodes acquire a thicker 
deposit than the inside surfaces, and the thickness of the de- 
posit decreases with the distance from the anodes. 

While for smooth articles the most suitable distance of the 
anodes from the object is 3^ to 5^ inches, for objects with 
depressions and hollows it must be larger, if it is not preferred 
to make use of the methods described later on. However, a 
deposit of a uniform thickness cannot be obtained by this 
means, because the portions nearer to the anodes will acquire 
a thicker deposit than the hollows ; hence the use of a small 
hand anode, which is connected by means of a thin flexible 
wire with the anode-rod, and introduced into the depressions 
and hollows, is to be preferred. This, of course, renders it 
necessary for a workman to stand alongside the bath and ex- 



DEPOSITION OF NICKEL AND COBALT. 209 

ecute the operation by hand ; but as the small anode can be 
brought within a few millimetres of the surface of the article, 
and at this distance slowly moved around it, a correspondingly 
thick deposit is in a short time formed. 

At any rate baths in which objects with depressions and. 
hollows are to be nickeled must possess greater resistance than 
baths for nickeling flat articles, and it is inexplicable why a 
bath with a large content of ammonium chloride and conse- 
quently slight conducting resistance can be recommended, as 
has been done, for nickeling hollow articles. 

In nickeling lamp-feet of cast-zinc, the use of the hand- anode 
can scarcely be avoided if the depressed portions also are to be 
provided with a uniformly good deposit. Moreover, zinc arti- 
cles form an exception to the general rule in so far as by reason 
of the highly positive properties of zinc, the resistance of the 
bath may be slighter than for baths for nickeling copper and 
its alloys, as well as iron and steel. 

Besides the above-mentioned general rules for nickeling, 
which also hold good for other electro-plating processes, the 
following may be given : — 

In suspending the objects in the bath, rub the metallic hooks 
or wires, with which they are secured to the rods, a few times 
to and fro upon the rod, in order to be sure that the place of 
contact is purely metallic. It is also well to acquire the habit 
of striking the rod a gentle blow with the finger every time 
when suspending an object, the gas-bubbles settling on the 
articles becoming thereby detached and rising to the surface. 
It is further advisable, before securing the objects to the object- 
rod, several times to move them up and down ; so to say, shake 
them beneath the fluid, whereby, on the one hand, the layers 
poorer in metal are mixed with those richer in metal, and, on 
the other, any dust which may float upon the bath and settle 
on the objects is removed. 

The objects suspended in the bath should not touch one 
another, nor one surface cover another, and thus withdraw it 
from the direct action of the anode. In the first case stains 
H 



210 ELECTRO-DEPOSITION OF METALS. 

will readily form on the places of contact, and in the latter the 
covered surface acquires only a slight deposit. That the ob- 
jects must not touch the anodes need scarcely be mentioned. 

Objects with depressions and hollows should be suspended 
in the bath so that the air in the hollows can escape, which is 
effected by turning the depressions upwards, or, if there are 
several depressions on opposite sides, by turning the articles 
about after being introduced into the bath. Air-bubbles re- 
maining in the hollows prevent contact with the solution, no 
deposit being formed on such places. 

It remains to say a few words in regard to the so-called polar- 
izing phenomena. In the theoretical part, it has been shown 
that by dipping two plates of different metals in a fluid a counter 
or polarizing current is generated, which is the stronger the 
further the two metals are removed from one another in the 
series of electro-motive force, and the more they differ in their 
electrical behavior. If the anodes in a nickel bath are of nickel 
and the articles of copper, the counter-current will be slight, 
because copper and nickel stand together in the series of 
electro-motive force (p. 15). The counter-current, however, 
becomes greater when iron objects are hung in the bath, and 
greatest with zinc surfaces which are to be nickeled, because 
zinc, being the most electro-positive metal, differs widely in its 
behavior from nickel. Now, since the counter-current flows in 
a direction opposite to that of the current introduced in the 
bath, the latter is weakened, and the more so the stronger the 
counter-current is. This explains why iron requires a stronger 
current for nickeling than copper-alloys, and zinc a stronger 
one than iron. 

Now it may happen that the counter-current becomes so 
strong as to entirely annul the effect of the principal current, 
and even to reverse the latter, the consequence being that, in 
the first case, the formation of the deposit is interrupted, and, 
in the latter, that the deposit is again destroyed, and the metals 
of which the articles consist dissolve and contaminate and spoil 
the bath. To avoid this, a main current must be conducted 



DEPOSITION OF NICKEL AND COBALT. 211 

into the bath, which, by its sufficiently large electro-motive 
force, can overcome the counter-current, and the consequences 
of the reversion of the current can be prevented by using the 
galvanometer and observing the deflection of its needle, which 
(according to p. 103) in proper time indicates the appearance 
of a reversed current. Now if a nickel-plater has only a slight 
current at his disposal, it follows from the above explanation 
that before nickeling the more electro-positive metals, such as 
iron, tin, zinc, it is best first to copper them, and thereby annul 
the action of these metallic surfaces as regards the formation 
of the counter-current. 

It happens comparatively seldom that the counter-current 
becomes so strong as to destroy the deposits formed, because 
for nickeling powerful Bunsen elements with two acids, or 
dynamo-electric machines with at least 4 volts' tension, are 
generally used. It is, however, well to acquaint the operator 
with all possible contingencies, and to explain the reason why 
the articles are preferably covered with a strong current. 
Sprague recommends an initial current of 5 volts tension, but 
in most cases one of 3.5 volts suffices for nickeling iron and 
copper alloys. 

Nickeling en masse of small and cheap objects. — This is 
effected by stringing the objects, if feasible, upon a copper wire, 
and placing a large glass bead between every two objects, to 
prevent the surfaces from sticking together in the bath. Such 
objects being generally only slightly nickeled, it suffices to 
allow them to remain for a few minutes only in the bath with a 
strong current, it being advisable to diligently shake the bun- 
dles in order to effect a change of position of the objects and 
prevent their touching one another, notwithstanding the glass 
bead placed between them. 

Very small objects, such as rivets, pins, etc., which cannot be 
strung upon wire, are nickeled in a stoneware dipping basket. 
To the bottom of the dipping basket is secured a copper or 
brass wire, which is connected with the object-rod, and the 
articles, not too many at a time, are then placed in the basket. 



212 



ELECTRO-DEPOSITION OF METALS. 



During the operation the articles must be constantly shaken, 
and as nickel baths, as a rule, do not conduct sufficiently well 
to properly nickel the objects in the basket, it is advisable to 
hold with one hand an anode connected by a flexible wire with 



Fig. 112. 




the anode-rod in the basket, while the other hand holds the 
sieve (Fig. 112) and constantly shakes and turns it. For 
nickeling in the dipping basket it is further advisable to heat 
the nickel bath. 

Fig. 113. 




In place of a stoneware dipping basket, a small shallow 
baskef of brass wire, Fig. 113, to which are soldered two cop- 
per wires for suspending it to the object-rod, may preferably be 



DEPOSITION OF NICKEL AND COBALT. 213 

used. From the soldered places a few copper wires extend to 
the bottom of the basket. To prevent the basket from be- 
coming covered with nickel it is coated with asphalt varnish. 
At a distance of about 2^ to 3 inches below the basket an 
anode is arranged in horizontal position, while with one hand 
a hand-anode is held over the small articles in the basket. By 
this arrangement a thicker deposit is more rapidly obtained, 
especially if with the other hand the articles are constantly 
stirred by means of a glass or wooden rod. 

Warren has described a solution of nickel and one of cobalt 
which can be decomposed in a simple cell apparatus. With 
the nickel solution, which was prepared by dissolving 100 parts 
by weight of nickel chloride in as little water as possible and 
mixing with a concentrated solution of 500 parts of Rochelle 
salts, no satisfactory results could be obtained. The cobalt solu- 
tion however yielded good results, and would seem to be suit- 
able for electro-plating small objects en masse. It will be 
further referred to under " Cobalting." 

In the last few years a number of contrivances for electro- 
plating small articles en masse have been patented, the articles 
to be plated being, as a rule, contained in a revolving perfo- 
rated drum. The drums of some of the contrivances are con- 
structed of non-conducting material so that the articles receive 
the current through copper or other metallic strips, which are 
secured in the inside walls of the drums, and are brought in 
various ways in contact with the source of current. In other 
contrivances, for instance, the apparatus of Smith & Deakin, 
metallic pins capable of being turned around the shaft, which is 
in contact with the negative pole of the source of current, reach 
to the layer of articles in the drum, and effect the re-conduction 
of the current. Since in the contrivances mentioned the anodes 
are placed outside of the drum, and the latter acts as a dia- 
phragm with great resistance, a very high tension is required 
for the production of the deposit, independent of the fact that 
the articles being in constant motion require an essentially 
higher tension. 



214 ELECTRO-DEPOSITION OF METALS. 

In another class of apparatus the six or eight-cornered drum 
is constructed of the same metal which is to be deposited. 
Every metal plate forming one side is insulated from the next 
plate. A commutator of special construction renders it pos- 
sible for the plates which, while the drum is revolving, occupy 
the lowest position and upon which the articles for the time 
being rest, to be brought into contact with the negative pole of 
the source of current, while the positive current is carried to 
the plates occupying a higher position, they, therefore, acting 
as anodes. In these apparatuses the high resistance due to 
the arrangement of the anodes on the outside is overcome, but 
the commutator with the sliding contact constitutes a very 
sensitive part of this form of construction. 

In the apparatus patented by Dr. George Langbein & Co. 
great resistance is avoided, while the construction is very simple. 

A perforated drum of non-conducting metal is secured to a 
metal-shaft of the same material which is to be deposited. 
The drum together with the shaft revolves in metallic bearings 
to which the positive current is conducted. Contact pins are 
screwed in the shaft and above them is placed an anode rolled 
into the form of a cylinder, which is secured by screwing back 
the contact pins, so that it constantly revolves with the shaft 
and the drum containing the articles to be plated. Two or 
three copper strips are inserted inside the drum and secured 
by screws. They are connected by means of a sliding contact 
upon the face of the drum with the negative pole and, hence, 
bring the articles in contact with the current. 

Pfanhauser recommends the plating drum shown in Fig. 114 
for plating small articles en masse. 

Upon an iron shaft ^ to ^ inch in diameter are secured at 
a suitable distance two square discs of wood rich in rosin but 
free from tannin. 

Around their circumferences is placed a tissue of thin brass or 
copper wire, with meshes as wide as possible, corresponding to 
the size of the articles, so that not a piece can fall through. 
An opening, best on one of the sides, is provided for the intro- 
duction of the articles. 



DEPOSITION OF NICKEL AND COBALT. 



5 



Upon one end of the shaft is keyed a pulley or crank for 
slowly revolving the drum (about 20 revolutions per minute) 
by means of the transmission or by hand. Upon the other 
end of the shaft is secured a sliding contact — a strip of sheet 
metal — similar to the brushes of a dynamo, which is connected 
with the object-pole of the source of current. To bring the 
wire tissue in contact with the current-conducting shaft several 
thick, flat wires are soldered to the shaft, and being carried 
longitudinally outside over the drum, are soldered on the 
opposite face of the latter to the shaft. These wires have the 
further object of supporting the slight wire tissue. The whole 
is finally laid in two wooden bearings secured to the vat so that 

Fig. 114. 




the drum dips nearly up to the shaft into the bath. The 
anodes on both sides should be as large as possible and 
arranged at a distance of about 5^ inches from the sides of 
the drum. 

The drum is moderately filled with articles and revolved. 
By the articles tumbling about the contact is constantly 
changed and they are plated on every side. By the constant 
friction of the articles against the wire tissue of the drum, the 
latter remains bright and sufficient contact is secured. If, how- 
ever, this friction should not suffice to keep the tissue bright, 
other means must be adopted. 

The contrivances described above, while suitable for electro- 



216 



ELECTRO-DEPOSITION OF METALS. 



plating small articles which it would be too expensive and 
time-consuming to string upon wires, are not adapted for 
plating such articles as rods, bicycle spokes, chains, etc., be- 
cause by the revolution of the drum they would become so 
inextricably tangled and bent that uniform plating would be 
impossible, independent of the fact that by arranging the 
anodes in the interior of the drum a short circuit is immedi- 
ately formed. 

For plating such articles Dr. George Langbein & Co. have 
patented a rocking apparatus which does not exhibit the above- 
mentioned evils. It consists of a semicircular drum of non-con- 
ducting material, which contains the articles and is in contact 

Fig. 115. 




with the negative pole. The drum makes rocking movements 
around a stationary anode whereby the articles, for instance, 
spokes, are rolled from one side to the other and then back 
again. By this arrangement the spokes are not jumbled to- 
gether as is always the case in closed revolving drums, a uni- 
form deposit upon all portions of the articles is effected, and 
the latter come with a beautiful lustre from the apparatus. 

For suspending bicycle spokes in the bath, Pfanhauser 
recommends the arrangement shown in Fig. 115. A deter- 



DEPOSITION OF NICKEL AND COBALT. 217 

mined number of spokes are at one time suspended in the bath, 
and by occasionally shaking them their position is altered in 
order to change the contact and produce uniform nickeling. 

Stripping nickeled articles. — Defective nickeling must, as a 
rule, be completely removed before the objects can be re- 
nickeled, since the second deposit adheres badly to the previous 
one, especially if the latter has become dry. The removal of a 
nickel-deposit is in most cases a disagreeable labor, which, 
however, can most assuredly be saved if the utmost care and 
painstaking cleanliness are observed in freeing the articles from 
grease, and in regulating the current. For the removal of the 
nickel coating the following stripping acid, which may be used 
either cold or tepid, has been recommended: Sulphuric acid 
of 66° Be., 4 lbs.; nitric acid of 40 Be., 1 lb.; water about 
1 pint. First put the water in a stoneware jar and cautiously 
add, a little at a time, the sulphuric acid, since considerable 
heat is generated when this acid is mixed with water. When 
the entire quantity of sulphuric acid has been added, pour in 
the nitric acid, when the bath is ready for use. In making up 
the stripping bath, the proportions of the acids may be varied, 
but the foregoing will be found to answer every purpose. An 
addition of 8 ozs. of potassium nitrate to the bath has also been 
recommended. 

When stripping nickel-plated articles in the above bath it is 
necessary to watch the operation attentively, since some articles 
are very lightly coated and a momentary dip is frequently 
sufficient to deprive them of their nickel. Other articles which 
have been thoroughly well nickeled, but require from some 
accidental cause to be stripped and re-nickeled, will need im- 
mersion for several minutes — indeed well-nickeled articles may 
occupy nearly half an hour in stripping before the underlying 
surface is entirely bare. The operation of stripping should be 
conducted in the open air, or in a fire- place, so that the acid 
fumes, which are very pernicious, can escape freely. The 
articles should be attached to a stout copper wire, and after a 
few moments' immersion should be removed from the bath to 



218 ELECTRO-DEPOSITION OE METALS. 

ascertain how stripping progresses. The moment it is found 
that the nickel has quite disappeared from every part, the 
article must be plunged into clean cold water. It is abso- 
lutely necessary that the work should not remain in the strip- 
ping solution one instant after the nickel is removed. When 
stripping has been properly effected, the underlying metal 
exhibits a bright, smooth surface, giving little evidence of the 
mixture having acted upon it. 

Many platers, however, prefer to remove the nickel-coating 
mechanically by brushing with emery. From depressions it is 
as much as possible removed with the brush, after which the 
object is freed from grease and pickled, and coppered before 
nickeling. In this case the layer of copper serves for cement- 
ing together the old and new deposits, and there will be no 
danger of the new deposit peeling off in polishing. 

It has also been proposed to remove the nickel from the arti- 
cles by means of the battery or dynamo-machine by making 
them the anodes in a nickel-bath ; but in this case a separate 
solution should be employed for the purpose. 

As a remedy against the yellowish tone of the nickeling, 
Pfanhauser recommends suspending the nickeled articles, im- 
mediately after taking them from the nickel bath, as anodes in 
a nickel bath acidulated with citric or hydrochloric acid, a 
piece of sheet nickel serving as the cathode, and to allow the 
current to act for a few seconds. It is claimed that thereby 
the basic nickel salts separated together with the nickel, and to 
which, according to Pfanhauser, the yellowish tinge is due, are 
dissolved and the nickeling will show a pure white tone. 

The following is a brief resume of the principal phenomena 
which may occur in nickeling, as well as the means of avoid- 
ing them : 

I. The articles do not become coated with nickel, but acquire 
discolored, generally darker, tones. Reasons : The current is 
either too feeble to effect the reduction of nickel, and the 
coloration is due to the chemical action of the nickel solution 
upon the metals constituting the objects. This phenomenon 



DEPOSITION OF NICKEL AND COBALT. 21 9 

is frequently observed in nickeling zinc articles. Remedy : 
Increase the current or diminish the area of suspended objects ; 
also examine whether the current actually passes into the bath, 
otherwise clean the places of contact. 

2. A deposition of nickel takes place, but it is dark or spotted 
or marbled, even with a sufficiently strong current. Reasons : 
The bath is either alkaline, which has to be ascertained by test- 
ing with litmus-paper, and, if so, the slightly acid reaction of 
the bath has to be restored by the addition of a suitable acid; 
or, the bath is too concentrated, in which case a separation of 
crystals will be observed — this is remedied by diluting with 
water; or, the nickel solution is very poor in metal, which can 
be remedied by the addition of nickel salt; it should also be 
tested as to the admixture of copper, the production of dark 
tones being frequently due to this — in this case the bath is 
allowed to work for some time, and if the content of copper is 
inconsiderable a white deposit will soon be obtained; or, the 
cleaning and pickling of the articles have not been thoroughly 
done, which is remedied by again cleaning them ; or, the con- 
ducting power of the bath is insufficient, which is remedied by 
the addition of a suitable conducting salt. 

When freshly prepared baths yield dark nickeling, it can 
generally be remedied by working the bath two or three hours. 

3. A yellowish tinge of the nickeling. Reasons : See under 
2 ; or, with cast-iron an insufficient metallic surface, which is 
remedied by repeating the scratch-brushing: or, unsuitable 
composition of the bath. 

4. The objects rapidly acquire a white deposit of nickel, but 
the color soon changes to dull gray-black, especially on the 
lower edges and corners. Reason : Too strong a current. Rem- 
edies : Regulating the current, or suspending more objects, or 
uncoupling elements. Frequent turning of the articles. 

5. The nickeling is white, but readily peels off by scratching 
with the finger-nail or by the action of the polishing wheel. 
Reasons: The current is too strong, which is remedied as under 
4; or, the bath is too acid — this is remedied by the addition of 



220 ELECTRO-DEPOSITION OF METALS. 

spirit of sal ammoniac, potassium carbonate, or nickel carbon- 
ate, according to the composition of the bath ; or, insufficient 
cleaning and pickling, which is remedied by thorough cleaning 
after removing the defective deposit, or, if it cannot be entirely 
removed, coppering. 

6. Though nickeling may proceed in a regular manner, some 
places remain free from deposit. Reasons : Either the surfaces 
of some of the objects touch one another, or air bubbles are 
inclosed in cavities ; or, faulty arrangement of the anodes. 
Remedy : Removal of the causes. 

7. The deposit appears with small holes. Reason; A deposit 
of particles of dust upon the objects. Remedy: Remove the 
dust from the surface. When there is a general turbidity of the 
bath in consequence of alkalinity, add the most suitable acid, 
and boil and filter the bath ; or, insufficient removal of gas 
bubbles from the objects. Remedy: Shake the object-rods by 
blows with the finger. 

8. Deposition takes place promptly upon the portions of the 
objects next to the anodes, while deeper portions remain free 
from nickel or become black ; or, the portions covered by the 
suspending wire show dark lines. Reason: Insufficient con- 
ducting power of the bath. With large depressions this can- 
not be remedied by the addition of a suitable conducting salt, 
but requires treatment with the hand-anode. 

Refreshing nickel baths. — According to their composition, 
the amount of work performed, and the anodes used, the baths 
will in a shorter or longer time require certain additions in 
order to keep their action constant. By " refreshing " is not 
understood the small addition of acid or alkali from time to 
time required for restoring the original reaction of the baths, 
but additions intended to increase the metallic content and 
diminished conductivity. 

The metallic content is increased by boiling the bath with 
some of the nickel salt used in its preparation, while the con- 
ductivity is improved by adding, at the same time, so much 
conducting salt as is necessary to restore the electro-motive 



DEPOSITION OF NICKEL AND COBALT. 221 

force originally required. Nothing definite can, of course, be 
said in regard to the quantity of such additions, it being advis- 
able to observe their effect on a small portion of the bath, so as 
to be sure not to spoil the entire bath. 

Nickel baths bear, as a rule, refreshing several times, but as 
in the course of time they take up impurities, even when the 
greatest care is exercised, it is best to refresh them at the 
utmost twice, and then to renew them entirely. 

The treatment of the articles after nickeling, as well as after 
all electro-plating processes, has already been described, and 
it is only necessary here to refer again to the fact, that with 
articles of iron and steel, immersion in boiling water before 
drying in saw-dust is absolutely necessary, and subsequent dry- 
ing in a drying chamber is also a great safeguard as regards 
stability and protection against rust. 

Nickel deposits are polished upon felt wheels or bobs of 
cloth, muslin, or flannel, with the use of Vienna lime, rouge, 
etc. (See " Polishing," page 148.) Sharp edges, corners, and 
raised portions should be held only with slight pressure against 
the polishing wheels, they being more strongly attacked by 
them than flat surfaces. Knife-blades and surgical instruments 
with sharp edges require special care in polishing, which will 
be referred to later on. 

After polishing, the nickeled objects, especially those with 
depressions, have to be freed from polishing dirt by brushing 
with hot soap-water or dilute hot caustic lye or benzine, then 
rinsed in hot water and dried in clean, fine saw-dust. 

Objects which are not required to be polished, but left matt, 
that is, just as they come out of the nickel bath, should be 
taken from the bath one at a time, and at once plunged into 
perfectly clean hot water for a few moments, and then placed 
aside to dry spontaneously. Matt nickel being very readily 
stained or soiled, even when touched with clean hands, the 
work should be handled as little as possible. 

Nickeling sheet zinc. — The nickeling of sheet zinc has been 
surrounded with a great deal of mystery by those engaged in 



222 ELECTRO- DEPOSITION OF METALS. 

its manufacture, which may, perhaps, be excusable on the 
ground that there is scarcely another branch of the electro- 
plating industry in which experience had to be acquired at the 
sacrifice of so much money and time as in this. Nevertheless, 
the nickeling of sheet zinc makes no greater demand on the in- 
telligence of the operator than any other electro-plating process, 
it requiring only an accurate consideration of the relations of 
the electric behavior of zinc towards nickel; consequently, a 
knowledge of the strength of the counter-current and of the 
chemical behavior of zinc towards the nickel solution, which 
may readily dissolve the zinc; further, a correct estimation of 
the current- intensity required for a determined zinc surface, as 
well as of the proper anode-surface, and the most suitable com- 
position and treatment of the nickel baths. 

With due observation of these relations, the nickeling of 
sheet zinc is accomplished as readily as that of other metals; 
and the suggestions to first cover the sheets in a bath with a 
strong current, and finish nickeling with a weaker current, or 
to amalgamate the zinc before nickeling, need not be considered. 

Below the conditions required for nickeling sheet zinc, and 
the execution of the process itself, together with the preliminary 
and final polishing of the sheets, will be found fully described. 

The preliminary grinding or polishing is effected upon broad 
cloth wheels (buffs) formed of separate pieces of cloth. The 
polishing lathes run with their points in movable bearings se- 
cured in a hanging cast-iron frame by a set screw and safety 
keys, or preferably as shown in Fig. 98, since with this con- 
struction an injury to the grinder by the lathe jumping out is 
impossible. 

The bobs, when new, have on an average a diameter of 12 to 
16 inches, and a width of 5 ^ to 8 inches. The principal point 
in the construction of these bobs is uniform weight on all sides, 
quiet running and the possibility of a good polish without 
great exertion depending on this. Bobs not well balanced run 
unsteadily and jump, thereby producing fine scratches upon the 
sheet. The bobs are constructed as follows : A square piece 



DEPOSITION OF NICKEL AND COBALT. 



223 



Fig. 116. 



of cloth is folded fourfold and the closed point cut off with a 
pair of scissors, so that on unfolding the cloth the hole produced 
by the cut is exactly in the centre of the cloth disk. According 
to the diameter of the spindle more or less is cut away, but in 
every case just sufficient for the piece of cloth to be conven- 
iently pushed upon the spindle. The latter, which is provided 
with a pulley and a hoop against which the pieces of cloth fix 
themselves, as well as with a nut and screw for securing them, is 
vertically fastened in a vise, and the separate pieces of cloth are 
pushed upon it so that the second piece placed in position 
forms an angle of about 30 (Fig. 116) 
with the first, the operation being thus 
continued until the bob has the desired 
width. Next a small, but very strong iron 
disk is laid upon the cloth bob, and the 
separate pieces are pressed together as 
firmly as possible with the screw. The 
spindle is then placed in the bearings, and 
after adjusting the belt upon the pulley the 
bob is revolved, a sharp knife being held against it to remove 
the projecting corners. In polishing sheet zinc the bobs make 
2400 to 3000 revolutions per minute, according to whether 
finely rolled or rougher sheets are to be polished. 

For the purpose of polishing or grinding, the operator places 
the sheet upon a support of hard wood of the same size and 
form as the sheet, and grasps the two corners of the sheet 
nearest to his body, together with the support, with the hands, 
applying with the balls of the hands the necessary pressure to 
hold the sheet upon the support. The lower half of the sheet, 
that furthest from the body, rests upon the knees of the opera- 
tor, and with them he presses the sheet against the polishing 
wheel, constantly moving at the same time, and at not too slow 
a rate, the knees from the right to the left, then from the left to 
the right, and so on. Previous to polishing, a streak^of oil 
about 2 inches wide is applied by means of a brush to the 
centre of the sheet in the visual line of the operator, and the 




224 



ELECTRO-DEPOSITION OF METALS. 



revolving bob is impregnated with Vienna lime by holding a 
large piece of it against it, when polishing of the lower portion 
of the sheet begins. When about f of the surface has thus 
been polished, the sheet is turned round and the remaining 
portion subjected to the same process. The sheet is then 
closely inspected to see whether there are still dirty or dull 
places, and, if such be the case, it is polished once more after 
moistening it with some oil and again impregnating the bob 
with Vienna lime. The sheet being sufficiently polished, the 
oil and polishing dirt are removed by dry polishing, after pro- 
viding the bob with sufficient Vienna lime, so that the sheets 
when finished show no streaks of dirt or oil. 

Fig. 117. 




Self-acting sheet polishing machines have been constructed by 
Dr. Sackur, F. Rauber, EliachofT, and others. Such machines 
give a very good polish, but have the disadvantage that thin 
sheets when polished upon some of them become wrinkled or 
wind up on the polishing roller. 

In order to explain the principle upon which these machines 
are constructed, a description of F. Rauber's sheet grinding and 
polishing machine is given. With this machine metallic sheets 
of any length can be polished. By the simultaneous lateral and 
longitudinal motion of the sheets a faultless polish is obtained, 
streaks and scratches being especially avoided. 



DEPOSITION OF NICKEL AND COBALT. 



225 



The machine essentially consists of the gearing A and the 
actual polishing machine B, Figs. 117, 118, 119. The gearing 




A consists of the two standards a a, the shaft b, a fast and loose 
15 



226 ELECTRO-DEPOSITION OF METALS. 

pulley, c c, the large driving-wheel d, a small driving-wheel, e, 
and the eccentric/. 

The polishing machine B consists of the wooden frame g with 
wcoden plate //, the two standards i i, the polishing roller k, 
the iron counter roller /, the expanding contrivance m y which is 
effected by means of three spiral springs, the gearing n with 
the rope-drum o, the rope with the tongs g, and the shaking 
arrangement x. 

The machine is set in motion by the engaging coupling x 
on the gearing A. The shaft of the gearing makes about 200 
revolutions per minute, and the polishing roller k is revolved 
by a belt from the driving-wheel d. At the same time the 
gearing n is set in motion by a belt from the driving-wheel ^, 
in consequence of which the rope is wound upon the drum 0, 
and the tongs on the rope draw the sheet to be polished under 
the polishing roller. If the sheet is to go back, the rope-drum 
is disengaged by means of the coupling y, and the polishing 
roller k, which moves lightly upon the counter-roller /, draws 
the sheet back. To prevent the sheet from jumping back, the 
brake r is provided on the rope-drum 0. By the treadle r, the 
workman is enabled to transport the sheet slowly or rapidly, 
as may be required. To move the sheet forward, the rope- 
drum is again engaged. The lateral motion of the sheet is 
effected by the shaking contrivance x. 

From the eccentric/, of the gearing A, the slide rod t is con- 
nected with the joint lever x and the latter by the pin s with the 
table plate h, whereby the latter when the machine is running 
is moved to the sides. 

The centre of motion of the table plate is upon the pin v. 
To regulate the pressure of the sheet against the polishing 
roller, the expanding arrangement m is placed under the table 
plate h. It consists of three vertical bolts with spiral springs, 
each of which can be screwed up and down by a nut. 

To facilitate the lateral motion of the table plate //, the bolts 
of the expanding contrivance m are provided with rolls which 
press against the plate. If the tension is sufficient and a sheet 



DEPOSITION OF NICKEL AND COBALT. 
Fig. 120. 



227 




228 



ELECTRO-DEPOSITION OF METALS. 



is to be introduced, it is only necessary to draw the table plate 
down by means of the treadle w, to push the sheet under the 
polishing roll k } and to engage the. tongs g. In front of the 
gearing A is a table for the reception of the sheet, as shown in 
the illustration. 

Fig. 1 20 shows an automatic sheet polishing machine con- 
structed by F. W. Koffler of Vienna. It has the advantage of 
the sheets passing entirely free through the machine, their 
surfaces acquiring a fine polish free from scratches. 

The machine works with two polishing rolls or buffs, A and 
B, Fig. 121, which revolve in the direction of the arrows. C 
is the polishing table upon which are mounted the two seg- 



FlG. 121. 




ments^/S for supporting the sheet, the two sliders SS n and the 
pairs of transporting rolls a b c. The sheet to be polished is 
at the entering place in front of the polishing roll A so deliv- 
ered to the machine that the transporting rolls a catch the 
sheet and push it under the polishing roll A> when it is polished 
by the latter. For the solid support of the sheet while being 
polished, the segments / and f, are provided, the sheet sliding 
over them in passing through the machine. When the end d 
of the sheet I has reached the transporting roll a, the polishing 
table is, by the gearing of the machine, raised from the polish- 
ing rolls A and B, as shown in Fig. 122, and the sliders SS, 
assume a horizontal position. By this position of the sliders 



DEPOSITION OF NICKEL AND COBALT. 



229 



SS n the sheet is prevented from rising and clinging to the 
polishing roll and the end d of the sheet is protected from 
being caught by the polishing roll. Since the transporting 



Fig. 122. 




rolls are in constant motion, the point e (the beginning of the 
sheet) will soon reach the transporting rolls c y Fig. 123, while 
the second succeeding sheet II, after the entering place has 
been released by the bolt *", is delivered to the machine, 



Fig. 123. 




reaches the vertex of the polishing roll A, and reversion by 
means of the mechanism of the machine having been accom- 
plished, the polishing table assumes its former position and the 
sheets are pressed with the required force on the polishing rolls. 
The polishing roll A operates upon two-thirds of the length 



230 ELECTRO-DEPOSrTION OF METALS. 

of the sheet from one end, and the polishing roll B upon two- 
thirds from the other end, so that the centre portion of the 
sheet is twice manipulated. Since the gearing of the machine 
requires uniform charging of the sheet, an automatic contriv- 
ance is provided whereby the entering place is at the proper 
time blocked by the bolt i, and again opened in order to de- 
liver another sheet to the machine. The operation described 
is then repeated and from 600 to 800 sheets can in ten hours 
pass through the machine. 

The automatic gearing can be arranged for lengths of 50, 
100, and 150 centimeters ( 19.C8, 39.37, and 59.05 inches), and 
sheets of different lengths may at the same time be polished. 

The rapidity with which the sheets are passed through the 
machine is regulated by interchangeable wheels, according to 
the quality and effect desired. 

The thinnest sheets (0.1 millimetre) can be polished upon 
this machine without danger of them puckering or clinging to 
the polishing roll. The machine is entirely constructed of 
iron. It is 8 feet 3.42 inches long, and 5 feet wide, and re- 
quires a power of 6 to 8 horse power, according to the condi- 
tion of the sheets to be polished. 

Fig. 124 shows an automatic sheet-polishing machine as 
constructed by Friedr. Krupp Grusonwerk, Magdeburg- 
Buckau, Germany. 

This machine serves for grinding and polishing sheets of 
brass, copper, nickel, zinc, nickel-zinc, and other metals of any 
thickness and in lengths up to 31.49 inches. 

It consists essentially of a polishing roll having a revolving, 
and at the same time a sliding, motion. This polishing roll 
consists of cloth, felt, leather, wood, etc., according to the 
nature, condition, and the desired exterior of the sheets to be 
ground or polished. The sheets are pushed forward by a large 
hollow roll placed vertically under the polishing table, this roll 
together with smaller transporting rolls connected with it by 
spur wheels, serving at the same time for supporting the sheets. 

The rapidity of the passage of the sheets through the ma- 



DEPOSITION OF NICKEL AND COBALT. 23 1 

chine is regulated, according to the thickness of the sheets and 




the degree of polish desired, by driving wheels which can be 
readily interchanged and by step pulleys of a connecting gear, 



232 ELECTRO-DEPOSITION OF METALS. 

and with uninterrupted work amounts to about 295 feet per 
hour. 

In order to exert with the large hollow pushing-roll a pres- 
sure corresponding to the degree of polish against the sheet 
lying upon it and against the polishing roll, its bearing is pro- 
vided with a lever of the first kind by which the pressure — 
also while the machine is running — is regulated by means of a 
screw. 

As soon as the machine is at rest, the pressure upon the 
polished sheet can be immediately released by a slight pres- 
sure of the foot upon the foot-lever, and the sheet taken from 
the machine, and another sheet introduced. 

Cleaning zinc sheets. — The sheets are best freed from grease 
in two operations, first dry and then wet. For the dry process 
use a very soft piece of cloth and, after dipping it in Vienna 
lime very finely pulverized and passed through a hair sieve, 
rub over the sheet in the direction of a right angle to the 
polishing streaks, applying a very gentle pressure. For the 
wet process, dip a moist piece of cloth or a soft sponge free 
from sand into a paste of impalpable Vienna lime, whiting and 
water, and go carefully over the sheet so that no place remains 
untouched. Then rinse the sheet under a powerful jet of 
water, best under a rose, being particularly careful to remove 
all the lime, going over the sheet, if necessary, with a soft, wet 
rag, and observing whether all parts appear evenly moistened. 
If such be the case, cleaning is complete, otherwise the sheet 
has to be once more treated with lime. 

If the sheets are to be nickeled on only one side, two of them 
are placed together with their unpolished sides and fastened on 
the two upper corners with binding screws to which is soldered 
a copper strip about 0.39 inch wide, by which they are sus- 
pended to the conducting rods. Plating is then at once pro- 
ceeded with, without allowing the sheets to remain exposed to 
the air longer than is absolutely necessary. Special care must 
be had that the lime does not dry, as this would produce stains 

Some manufacturers nickel the cleansed sheets without pre- 



DEPOSITION OF NICKEL AND COBALT. 233 

vious coppering or brassing, and claim special advantages for 
such direct nickeling. This may be done with a bath of nickel 
sulphate and potassium citrate without, or with a greater or 
smaller addition of, sal ammoniac, according to the area to be 
nickeled and the intensity of current at disposal. However, 
sheet zinc directly nickeled does not show the warm full tone 
of sheets previously coppered or brassed ; besides, direct 
nickeling requires a far more powerful current, so that it is not 
even more economical. 

For the nickeling process itself, it is indifferent whether the 
sheets are previously coppered or brassed, but the choice be- 
tween the two is controlled by a few phenomena which must be 
mentioned. The nickel deposit upon brassed sheets shows a 
decidedly whiter tone than that upon coppered sheets, and 
brassing would deserve the preference if this process did not 
require extraordinarily great care in the proper treatment of 
the bath, the nickel deposit readily peeling off, generally in the 
bath itself, which seldom or never occurs with coppered sheet, 
and then may generally be considered due to insufficient clean- 
ing or other defective manipulation. 

This peeling off of the nickel deposit may be prevented by 
giving due consideration to the conditions, and avoiding, on the 
one hand, too large an excess of potassium cyanide in the brass 
bath, and, on the other, by regulating the current so that no 
pale yellow or greenish brass is precipitated. Since nickeling 
with a strong current requires only a few minutes for a deposit 
of sufficient thickness capable of bearing polishing, it is gener- 
ally desired to brass the sheets at the same time, so that the 
operation may proceed rapidly and continuously. To do this, 
a very powerful current has to be conducted into the brass bath, 
the result being that a deposit with a larger content of zinc and 
a correspondingly lighter color is formed, but also with a 
coarser, less adherent structure, and this is the principal reason 
why the nickel deposit, together with the brass deposit, peels 
off. To avoid this, the brassing must be done with a current 
so regulated that the deposit precipitates uniformly, adheres 



234 ELECTRO-DEPOSITION OF METALS. 

firmly, and is not porous, the correct progress of the operation 
being recognized by the color being more like tombac, and not 
pale yellow or greenish. Where brassing has to be done quickly 
the content of copper in the brass bath must be increased to 
such an extent that a powerful current produces a deposit of 
the above-mentioned color, and, hence, too large an excess of 
potassium cyanide must be strictly avoided. 

It will be seen that brassing requires a certain attention 
which is not necessary in coppering, and therefore the latter is 
to be preferred. 

For coppering one of the baths, III. or V., given under 
" Deposition of Copper" can be used, to which, for this 
special purpose, more potassium cyanide may be added. 
The sheets should remain in this bath no longer than required 
to uniformly coat them with a beautiful red layer of copper, 
and under no circumstances must they be allowed to remain 
until the coppering commences to become dull or even dis- 
colored. They should come from the bath with a full, or 
at least half, lustre. When taken from the copper bath the 
sheets are thoroughly rinsed in a large water reservoir, the 
contents of which must be frequently renewed, care being had 
to remove any copper solution adhering to the unpolished sides 
which are not to be nickeled, since that would soon spoil the 
nickel bath. The sheets are then immediately brought into the 
nickel bath, it being best to suspend two, three, or four of them 
at the same time, to prevent one from being more thickly nick- 
eled than the other, and take them out the same way. In sus- 
pending the sheets in the bath, care should be had to bring them 
as soon as possible in contact with the conducting rod, a neglect 
of this rule being apt to produce blackish streaks and stains. 

Every separate nickel bath in which sheets are to be nickeled 
must be fed with the full current of a dynamo-machine, one of 
250 to 300 amperes with 4 volts' tension being generally used. 
According to the number of sheets, generally 6 to 8, each 20x20 
inches, to be nickeled, the dimensions of the vats are as follows : 
63 inches long, 15^ inches wide, and 25^ inches deep, or, 83 



DEPOSITION OF NICKEL AND COBALT. 235 

inches long, 15^ inches wide, and 25^ inches deep. One to 
two minutes suffice to give 6 sheets a sufficiently thick deposit 
of nickel with a dynamo-machine of the above-mentioned capa- 
city, and 2 to 3 minutes for eight sheets ; and it may be accepted 
as a rule that, with a bath of good conductivity, a density of cur- 
rent of from 1.4 to 1.5 amperes and 5 volts' tension is required 
per 15.5 square inches of zinc surface for the solid nickeling of 
the sheets. For nickeling zinc in baths conducting with diffi- 
culty, for instance, a simple solution of sulphate of nickel and 
ammonia without the addition of conducting salts, or in baths 
containing boric acid, 1.3 to 1.4 amperes and 6 to 7 volts, must 
be allowed per 15.5 square inches of zinc surface if the nickel- 
ing is to be effected in the above named space of time. A den- 
sity of current of 1.4 to 1.5 amperes and 4 to 4^ volts, at which 
the sheets have to remain in the bath for 3 minutes, is the most 
suitable, the deposit thus obtained being in every respect fault- 
less, provided the nickel bath is of proper composition. 

For nickeling sheet zinc, rolled anodes are, as a rule, only 
used, except when working with baths containing boric acid. 
The anode surface must at least be equal to that of the zinc 
surface. The distance between the anodes and the sheets 
should be from 3 to 3^ inches, and when the current-strength 
is somewhat scant the distance may be reduced to 2^ inches. 
The nickel anodes have to be taken from the bath once daily 
and scoured bright with scratch-brushes and sand. For the 
rest, all the rules given for nickel anodes are valid. 

Baths used for nickeling sheet zinc soon become alkaline in 
consequence of the powerful current used, which is shown by 
red litmus-paper turning blue. The alkalinity also manifests 
itself by the bath becoming turbid and the nickeling not turn- 
ing out pure white. The slightly acid reaction required is 
restored by citric acid solution. The appearance of the dreaded 
black streaks and stains is due either to the current itself being 
too weak or, to its having been weakened by an extremely 
great resistance of the nickel bath; also to an insufficient me- 
tallic surface of the anodes, which may be either too small or 



236 ELECTRO-DEPOSITION OF METALS. 

not sufficiently metallic on account of tarnishing; and finally 
to an excessive alkalinity of the bath or insufficient contact of 
the hooks with the connecting rods. 

The metallic content of the bath must from time to time be 
augmented by the addition of nickel salt, and the bath filtered 
at certain intervals. When the conductivity abates, it has to 
be restored by the addition of conducting-salt. 

When the sheets have been sufficiently nickeled, they are 
allowed to drain off, then plunged into hot water, and, after re- 
moving the binding-screws, dried by gentle rubbing with fine 
sawdust free from sand and passed through a fine sieve to 
separate pieces of wood. In all manipulations, the unnickeled 
sides are placed together, while a piece of paper of the size and 
form of the sheets is laid between the nickeled sides. 

The nickeled sheets are finally polished, which is effected by 
placing them upon supports and pressing against the revolving 
bob as previously described, the sheets being, however, only 
moderately moistened with oil, and not too much Vienna lime 
applied to the bob. Polishing is done first in one direction and 
then in another, at a right angle to the first. After polishing, 
the sheets are finally cleansed with a piece of soft cloth and 
impalpable Vienna lime, when they should show a pure white 
lustrous nickeling, free from cracks and stains, and bear bend 
ing and rebending several times without the deposit of nickel 
breaking or peeling off. 

Nickeling tin plate. For elegant and durable nickeling, tin- 
plate also requires previous coppering. The deposit is effected 
with a less powerful current than for sheet zinc. Scouring is 
done as described for sheet zinc, also polishing of the nickeled 
tin-plate. 

Nickeling copper and brass sheets. The treatment of these 
sheets differs from that of sheet zinc in that the rough sheets 
are first brushed with emery and then polished with the bob. 
After treating the sheets with hot caustic lye or lime-paste, 
they are pickled by brushing them over with a solution of 1 
part of potassium cyanide in 20 parts of water. They are then 



DEPOSITION OF NICKEL AND COBALT. 237 

thoroughly and rapidly rinsed and immediately brought into 
the bath. To avoid peeling off, the current must not be too 
strong. 

Nickeling sheet- iron and sheet- steel. — Only the best quality of 
sheet should be used for this purpose. After rolling, the 
sheets are freed from scales by pickling, then passed through 
the fine rolls, and finally again pickled. If the nickeled sheets 
are not to exhibit a high degree of polish, it suffices to brush 
them before nickeling with a large, broad, fibre brush (p. 145) 
and emery No. 00. But for a high lustre, such as is generally 
demanded, the sheets have first to be ground. For fine grind- 
ing the pickled sheets, broad massive wheels of poplar wood 
are used, which are covered with leather and turned like the 
wheels described on p. 142. These wheels are 10 to 12 inches 
in diameter, and 2 to 4 or more inches long, according to the 
size of the sheets. For the first grinding, the wheels are coated 
with glue and rolled in emery No. 100 to 120, according to the 
condition of the sheets, while emery No. 00 is applied to the 
wheels used for the fine grinding. The grinding is succeeded 
by brushing, as described on p. 144. 

After preparing a sufficiently smooth surface, the sheets are 
at once rubbed with a rag moistened with petroleum, or, if 
preferred, with a rag and pulverized Vienna lime. They are 
then scoured wet in the manner described for sheet-zinc, p. 232. 
The scouring material must be liberally applied, especially if 
the sheets are to be directly nickeled without previous copper- 
ing, as is advisable. After rinsing off the lime-paste, the sheets 
are brushed over with very dilute sulphuric acid (1 part acid 
to 25 water), rinsed off, then lightly brushed over once more 
with lime-paste, again carefully rinsed, and immediately brought 
into the nickel bath. 

The current should be neither too strong nor too weak, but 
regulated so that the deposit of nickel is of sufficient thickness 
in 15 to 20 minutes without showing a tendency to peel off. 
It is not advisable to try to obtain a heavy deposit in a shorter 
time, because it would lack density, which is the principal re- 
quirement for nickeled sheet-iron. 



238 ELECTRO-DEPOSITION OF METALS. 

After nickeling, the sheets are rinsed in clean water, then 
plunged into hot water and dried by rubbing with warm saw- 
dust. After this operation, it is recommended to thoroughly 
dry the sheets in an oven heated to between 176 and 212° F. ? 
to expel any moisture from the pores, and then to polish them 
with Vienna lime and oil, or with rouge. 

Nickeling wire. Nickeling of wire of iron, brass, or copper 
is scarcely ever done on a large scale. It is, however, believed 
that the nickeling of iron and steel wires — for instance, piano- 
strings — might be of advantage to prevent rust or at least to 
retard the commencement of oxidation as long as possible. 

To nickel single wires cut into determined lengths, according 
to the general rules already given, is simple enough ; but this 
method cannot be pursued with wire several hundred yards long, 
rolled in coils, as it occurs in commerce. Nickeling the wire in 
coils, however, cannot be done, as only the upper windings ex- 
posed to the anodes would acquire a coat of nickel. Hence it 
becomes necessary to unwind the coil, and for continuous 
working pass the wire at a slow rate through the cleansing and 
pickling baths, as well as the nickel bath, and hot water reser- 
voir, as shown in Fig. 125, in cross-section, and in Fig. 126, in 
ground plan. 

The unwinding of the wire is effected by a slowly revolving 
shaft, upon which the nickeled wire again coils itself; but in the 
illustration the shaft is omitted. In Fig. 126 four wires run 
over the four rolls a, mounted upon a common shaft, to the 
rolls b upon the bottom of the vat A y whereby they come in 
contact with a thickly-fluid lime-paste in the vat, and are freed 
from grease. From the rolls b the wires run through the 
wooden cheeks t, lined with felt, which retain the excess of 
lime-paste, and allow it to fall back into the vat. The wires 
then pass over the roll c to the roll d. Between these two rolls 
is the rose g> which throws a powerful jet of water upon the 
wires, thereby freeing them from adhering lime-paste. The 
roll d, as well as its axis, is of brass, and to the latter is con- 
nected the negative pole of the battery or dynamo, so that by 



DEPOSITION OF NICKEL AND COBALT. 



2 39 



carrying the wires over the roll d negative electricity is con- 
ducted to them. From the roll d the wires run over the roll- 







o* 



■fl- 









«,i£i\ 




f? f f 



bench s (Fig. 125) to the vat C, which contains the nickel 
solution, so that they are subjected to the action of the anodes 



240 ELECTRO-DEPOSITION OF METALS. 

arranged in this vat on both sides of the wires. The wires then 
pass over the roll e, are rinsed under the rose h, and run finally- 
through a hot water reservoir and sawdust (these two appara- 
tuses are not shown in the illustration), to be again wound in 
coils. In case a high polish is required, the nickeled wires 
may be run under pressure through leather cheeks dusted with 
Vienna lime. 

Nickeling wire-gauze. — Messrs. Louis Lang & Son obtained, 
in 1 88 1, a patent for a method of nickeling wire-gauze, or wire 
to be woven into gauze, more especially for the purpose of 
paper manufacture. These wires, which are generally of copper 
or brass, are liable to be attacked by the small quantities of 
chlorine which generally remain in the paper pulp, by which 
the gauze wire eventually suffers injury. To nickel wire before it 
is woven, it is wound on a bobbin and immersed in a nickel bath 
in which it is coated with nickel in the usual way. It is then 
unwound and rewound on to another bobbin, and reimmersed 
in a nickel bath, as before, so as to coat such surfaces as were 
in contact with each other and with the first bobbin. To de- 
posit nickel on the woven tissues it may either be coated in its 
entire length, as it leaves the loom, or in detached pieces. For 
this purpose the wire gauze is first immersed in a pickel bath, 
and next in the nickel solution. On leaving the latter it is 
rinsed and then placed in a hot air chamber, and when 
thoroughly dry may be rolled up again ready for use. 

Nickeling knife-blades, sharp surgical instruments, etc. Con- 
siderable trouble is frequently experienced in nickeling sharp 
edged instruments, the edges and points being spoiled either 
by the deposit of nickel or in polishing. And yet such instru- 
ments can be readily nickeled in such a manner that the edges 
remain in as good condition as before. 

If new instruments which have never been used are to be 
nickeled, no special preparation is required, it being only 
necessary to free them at once from grease and bring them into 
the bath. But instruments which have been used or, by bad 
treatment have become partly or entirely covered with rust, 



DEPOSITION OF NICKEL AND COBALT. 241 

must be first freed from rust by chemical or mechanical treat- 
ment, and then polished. The marks left by the stone or emery 
wheel are effaced by means of the circular brush, this treatment 
being necessary to obtain perfect nickeling. But in brushing 
the edges are rendered dull if special precautionary measures 
are not used. For instance, the edge of a knife-blade must 
never come in contact with the brush. This is prevented by 
firmly pressing the blade flat upon a soft support of felt or 
cloth, so that the edge sinks somewhat into the support, with- 
out, however, cutting into it. The edge is then held downward, 
and thus together with the support brought against the revolv- 
ing brush. In this manner the blades may be vigorously 
brushed without fear of spoiling the edges. 

The treatment in giving them a high polish after nickeling is 
the same. Freeing from grease may be done in the usual 
manner with lime-paste ; but must also be effected upon a soft 
support, the same as in polishing. After thorough rinsing in 
clean water the separate pieces, without being previously cop- 
pered, are brought directly into the nickel bath, the composi- 
tion of which must, of course, be suitable for nickeling steel 
articles. The instruments are first coated with the use of a 
strong current, so that the deposition takes place slowly and 
with great uniformity. 

In suspending the articles in the bath, care should be had 
that neither a point nor an edge is turned towards the anodes. 
It is best to use a bath with anodes on one side only, and to 
suspend the blades with their backs towards the anodes. If, 
for any reason, the instruments are to be suspended between 
two rows of anodes, the edges should be uppermost, as near as 
possible to the level of the bath ; but they should never hang 
deep or downwards. 

The plated instruments are given a fine lustre by polishing, 
but during this operation they must always be exposed upon 
a soft support, as above described, to the action of a felt wheel, 
or, still better, of a cloth bob. 

In nickeling skates it is advisable to suspend them so that the 
16 



242 ELECTRO-DEPOSITION OF METALS. 

runners hang upwards and that the running surfaces are level 
with the surface of the bath, because if the deposit upon the 
running surfaces is too thick, it peels off readily when injured 
by grains of sand upon the ice. 

Nickeling printing plates ( electrotypes, cliches, etc. ) The ad- 
vantages of nickeling electrotypes, etc., over steeling will be 
referred to under " Steeling," and hence only the most suitable 
composition of the nickel baths and the manipulations required 
will here be given. 

The nickel baths according to formula I. (page 190) and 
formula VII. (page 193) are the most suitable for simple 
nickeling, because the ammonium sulphate not being present 
in too great an excess, as well as the presence of boric acid, 
causes the nickel to separate with considerable hardness. With 
nickeled electro-plates three times as large an addition can be 
printed as with plates of the same material not nickeled. 

It being a well-known fact that a fused alloy of nickel with 
cobalt possesses greater hardness than either of the metals by 
themselves, experiments proved that an electro-deposited nickel- 
cobalt alloy exhibited the same behavior, the greatest degree 
of hardness being attained with an addition of cobalt varying 
between 25 and 30 per cent. For this deposit the term hard 
nickeling is proposed, the most suitable baths for the purpose 
being prepared according to the following formulae : 

I. Nickel-ammonium sulphate 21.16 ounces, cobalt-ammon- 
ium sulphate 5.29 ounces, ammonium sulphate 8.8 ounces, 
water 10 to T2 quarts ; or, 

II. Nickel-ammonium sulphate 21.16 ounces, cobalt ammon- 
ium sulphate 5.29 ounces, crystallized boric acid 10.58 ounces, 
water 10 to 12 quarts. 

Bath No. I. is prepared by simply dissolving the salts in hot 
water, and, in case the bath is too acid, adding spirits of sal 
ammoniac until blue litmus paper is only slightly reddened. 
It is best to use rolled and cast anodes in equal proportions ; 
and when the bath becomes alkaline to restore its original 
slightly acid reaction by the addition of citric acid. 



DEPOSITION OF NICKEL AND COBALT. 



243 



To prepare bath No. II. dissolve the constituents by boiling; 
and in case not entirely neutral metallic salts have been used, 
add to the hot solution, with constant stirring, 1 to 1 ^ ounces 
of nickel carbonate for the neutralization of free sulphuric acid 
which may be present. This bath must not be neutralized, but 
worked with its strongly acid reaction, mixed anodes being 
also used. 

The bath prepared according to formula No. II. deserves the 
preference, it yielding a harder deposit than bath No. I. 

Fig. 127. 




For the rest, the treatment of the baths is the same as that 
given for nickel baths of similar composition ( pp. 190 and 193), 
and the process of hard nickeling does not essentially differ 
from ordinary nickeling. The suspending hooks are soldered 
to the backs of the plates by means of the soldering-iron and a 
drop of tin ; or the plates are secured in holders of sheet-cop- 
per 0.1 1 inch thick, and j{ to 1 inch wide, of the form shown 
in Fig. 127. The printing surface is freed from grease by 
brushing with lime-paste, rinsing in water, and then brushing 



244 ELECTRO-DEPOSITION OF METALS. 

with a clean brush to remove the lime from the depressions. 
The plates are then hung in the bath and covered with a strong 
current. When everywhere coated with nickel the current is 
weakened and the deposit allowed gradually to augment. 
With an average duration of nickeling of 15 to 20 minutes, 
with 2.8 to 3 volts, the deposit will, as a rule, be sufficiently 
resisting. 

The nickeled plates are rinsed in water, then plunged in hot 
water, and dried in sawdust, when the nickeled printing surface 
may be brushed over with a brush and fine whiting, it being 
claimed that plates thus treated take printing-ink better, while 
the first impressions of plates not brushed with whiting are 
somewhat dull. 

Nickel-facing is especially suitable for copper plates for 
color-printing, the nickel not being attacked like copper or 
iron by vermilion. 

Recovery of nickel from old baths. — At the present price of 
nickel its recovery from old solutions scarcely pays. The use- 
lessness of the bath is in most cases due to two causes: It has 
either become too poor in metal or it contains foreign metallic 
admixtures. In the first case, the expense of evaporating with 
the further manipulation is out of proportion to the value of the 
nickel recovered ; and, in the second case, the reduction of the 
foreign metals is inconvenient and connected with expenses 
which make it unprofitable. 

Urquhart proposes the following plan for recovering nickel 
from old solutions : Make a saturated solution of ammonium 
sulphate in warm water, and add to it the old nickel-plating 
solution with constant stirring, and, after the lapse of a few 
minutes, a granular precipitate of the double sulphate of nickel 
and ammonium will begin to separate. The addition of am- 
monium sulphate should be continued from time to time until 
the liquid is colorless. The precipitated salt is very pure, and 
may be used directly in making a new bath. 

To improve defective nickeling. — With the basis-metal thor- 
oughly cleansed defective places should not occur, but when 



DEPOSITION OF NICKEL AND COBALT. 245 

they happen, by accident or negligence, recourse is to be had 
to " doctoring." The " doctor" is arranged as follows : A piece 
of stout copper wire is bent in the form of a hook at each end, 
and a fragment of nickel anode is fastened firmly to one of the 
hooks with a piece of twine. The fragment of anode is then 
wrapped in several folds of muslin, the second hook connected 
by a wire to the anode-rod of the bath, and the article put in 
contact with the negative electrode. The rag end is now 
dipped in the nickel bath, applied to the defective spot, and 
allowed to rest upon it for a few moments, then dipped again 
and reapplied. By repeatedly dipping the rag in the nickel 
bath and applying it in this way, a sufficient coating of nickel 
may be given in a few minutes ; and if the operation is skill- 
fully performed, no trace of the patch will be observable after 
polishing. 

Nickeling by contact and boiling. — Franz Stolba has described 
a nickeling process by contact, which is executed as follows : — 

In a bright copper kettle heat to boiling a concentrated so- 
lution of zinc chloride with an equal or double the volume of 
soft water, and then add drop by drop pure hydrochloric acid 
until the precipitate formed by diluting the zinc chloride solu- 
tion with water disappears. Then add as much zinc powder as 
will lie upon the point of a knife, the effect of this addition be- 
ing that the copper of the kettle so far as it comes in contact 
with the solution is in a few minutes zincked. Now bring into 
the kettle sufficient nickel salt, best nickel sulphate, to color 
the fluid perceptibly green. Then introduce the articles to be 
nickeled together with small pieces of sheet zinc or zinc wire, 
so as to present many points of contact, and continue boiling. 
With a correct execution of the process it is claimed the articles 
will be uniformly nickeled in 15 minutes. If such is not the 
case, the boiling must be continued, fresh pieces of zinc added, 
or, if the solution does not appear sufficiently green, fresh nickel 
salt introduced. 

For the success of the process several conditions are neces- 
sary. The metallic articles must be thoroughly freed from 



246 ELECTRO-DEPOSITION OF METALS. 

grease, as otherwise no deposit of nickel is formed on the 
greasy places. In boiling, the solution must not become turbid 
by the separation of basic zinc salt, nor acid by free hydro- 
chloric acid, otherwise the nickeling will be dull and blackish. 
Hence, any turbidity must be at once removed by adding drop 
by drop hydrochloric acid, and too great acidity by the careful 
addition of solution of carbonate of soda. The articles thus 
nickeled are to be thoroughly washed with water, dried, and 
polished with whiting. 

Since stains are readily formed by this process, especially 
when nickeling polished iron and steel articles, on the places 
where the metal to be nickeled comes in contact with the zinc, 
Stolba in later experiments omitted the zinc, and thus the con- 
tact process becomes a boiling process. To a 10 per cent, 
solution of zinc chloride add enough nickel sulphate to give the 
solution a deep green color and then heat, best in a porcelain 
vessel, to the boiling-point. Then without troubling about the 
turbidity of the bath caused by the separation of a basic zinc 
salt, immerse the objects, previously cleansed and freed from 
grease, in it in such a way that they do not touch each other, 
or at least in only a few places, and keep the whole boiling 30 
to 60 minutes, from time to time replacing the water lost by 
evaporation. The after-treatment is the same as given above 
for the contact process. The deposit of nickel is, of course, 
very thin. 

This process, while suitable for the amateur, cannot be 
recommended to the professional electro-plater, the results not 
being sufficiently sure. A thin deposit of nickel of a light 
color may be obtained upon brass articles, but that upon iron 
articles is dark and mostly stained. 

Small articles, which are not to be nickeled by the electric 
current, are preferably coated by contact with cobalt by the 
process to be described later on, under " Deposition of cobalt." 
The higher price of cobalt salts makes little difference, small 
quantities only being required, and the color of cobalt can 
scarcely be distinguished from that of nickel. 



DEPOSITION OF NICKEL AND COBALT. 247 

By boiling a solution of 8^ ozs. of nickel-ammonium sul- 
phate and 83^ ozs. of ammonium chloride in 1 quart of water, 
together with clean iron filings free from grease, and introduc- 
ing into the fluid copper or brass articles, the latter become 
coated with a thin layer of nickel capable of bearing light 
polishing. The nickel solution has to be frequently renewed. 

According to experiments made by Dr. George Langbein, 
it is more advantageous to substitute a small piece of alumin- 
ium sheet for the iron filings and to touch with it the articles 
to be nickeled in a hot bath (about 185 to 194 F.) Or, 
string small articles upon an aluminium wire, though if this 
cannot be had, zinc wire may be used. 

According to R. Kaiser, an alloy containing nickel may be 
deposited upon articles by proceeding as follows : Melt J part 
of copper and 5 of tin, and granulate the fused mass by pour- 
ing it through a heated sheet-iron sieve into a bucket filled 
with water. Boil the granulated metal thus obtained with 
tartar free from lime, and add for every 100 parts by weight of 
granulated metal 0.5 part of nickel oxide previously ignited. 
Then bring the brass or copper articles, previously freed from 
grease and pickled, into the boiling fluid, and after boiling for 
a short time they will appear coated with a white alloy re- 
sembling German silver. The addition of nickel oxide must 
be repeated from time to time. Iron and steel articles are to 
be previously coppered. By adding nickel carbonate to this 
bath, it is claimed, coats richer in nickel and of a darker color 
than that of platinum to blue-black are obtained. 

Deposits of nickel alloys. — From suitable solutions of the me- 
tallic salts nickel may be. deposited together with copper and 
tin, as well as with copper and zinc. With the first combina- 
tion, especially, all tones from copper-red to gold-shade may 
be obtained, according to which metal predominates, or accord- 
ing to the current-strength which is conducted into the bath, 
as is also the case in brassing. 

A suitable bath for coating metallic articles with an alloy of 
nickel, eopper, and tin, for which the term nickel-bronze is pro- 



248 ELECTRO- DEPOSITION OF METALS. 

posed, is obtained by dissolving the metallic phosphates in 
sodium pyrophosphate solution. By mixing solution of blue 
vitriol with solution of sodium phosphate, cupric phosphate is 
precipitated which is filtered off and washed. In the same 
manner nickel phosphate is prepared from a solution of nickel- 
sulphate. These phosphates are then, each by itself, dissolved 
in a concentrated solution of sodium pyrophosphate, while 
chloride of tin is directly dissolved in sodium pyrophosphate 
until the turbidity, at first rapidly disappearing, disappears but 
slowly. 

Nothing definite can be said in regard to the mixing propor- 
tions of these three solutions, because the proportions will have 
to be varied according to the desired color of the deposit. The 
operator, however, will soon find out of which solution more 
must be added in order to obtain the tone desired. 

For depositing an alloy of nickel, copper, and zinc, solutions 
of cupric sulphate (blue vitriol) and zinc white in potassium 
cyanide, to which is added an ammoniacal solution of nickel 
carbonate, may be advantageously used. 

According to a French process, a deposit of German silver 
may be obtained as follows : Dissolve a good quality of German 
silver in nitric acid and add, with constant stirring, solution of 
potassium cyanide until all the metal is precipitated as cyanide. 
The precipitate is then filtered off, washed, dissolved in potas- 
sium cyanide, and the solution diluted with double the volume 
of water. This process, however, does not seem very feasible, 
since nickel separates with difficulty from its cyanide combi- 
nation. 

Watt recommends the following method : Cut up into small 
pieces sheet German silver about 1 oz., place the strips in a 
glass flask, and add nitric acid diluted with an equal bulk of 
water. Assist the solution of the metal by gentle heat. When 
red fumes cease to appear in the bulb of the flask, decant the 
liquor and apply fresh acid, diluted as before, to the undissolved 
metal, taking care to avoid excess ; it is best to leave a small 
quantity of undissolved metal in the flask, by which an excess 



DEPOSITION OF NICKEL AND COBALT. 249 

of acid is readily avoided. The several portions of the metallic 
solutions are to be mixed and diluted with about 3 pints of 
cold water in a gallon vessel. Next dissolve about 4 ozs. of 
carbonate of potash in a pint of water, and add this gradually 
to the former, with gentle stirring, until no further precipitation 
takes place. The precipitate must be washed several times 
with hot water, and then redissolved by adding a strong solu- 
tion of cyanide, with stirring, and about 1 oz. of liquid ammonia. 
To avoid adding too great an excess of cyanide, it is a good 
plan, when the precipitate is nearly all dissolved, to let it rest 
for half an hour or so, then decant the clear liquor, and dis- 
solve the remainder of the precipitate separately. A small ex- 
cess of cyanide solution may be added as "free cyanide," and 
the whole mixed together and made up to one gallon with cold 
water. The solution should then be filtered or allowed to re- 
pose for about 12 hours, and the clear liquor then carefully 
decanted from any sediment which may be present from cyanide 
impurities. The bath must be worked with a German silver 
anode, which should be of the same quality as that from which 
the solution is prepared ; a Bunsen battery should be employed 
as the source of electricity, or a dynamo-machine. 

Examination of Nickel-Baths. 

The reactions of the nickel baths have previously been briefly 
referred to, but the subject must here be more closely consid- 
ered. 

For the determination of the content of acid, a different 
method must be adopted according to the composition of the 
bath, i. e., whether it has been prepared with an addition of 
citric acid, boric acid, etc. The reddening of blue litmus paper 
simply indicates the presence of free acid in the bath, but leaves 
us in the dark as to which acid is present, and as to its deriva- 
tion. 

If, for instance, in consequence of insufficient solution of 
nickel, free sulphuric acid appears on the anodes, the bath be- 
comes at the same time poorer in nickel in proportion to the 



25O ELECTRO-DEPOSITION OF METALS. 

increase in the content of free sulphuric acid. If we have to 
deal with a bath prepared from nickel ammonium sulphate with 
an addition of ammonium sulphate, but without organic acids, 
the reddening of blue litmus paper will at once indicate a con- 
tent of free sulphuric acid, if the bath was neutral in the begin- 
ning. It is, however, quite a different matter when a bath con- 
taining boric acid is examined. In the formulae for preparing 
these baths, it has been seen that before adding the boric acid, 
any free sulphuric acid of the nickel salt present is to be re- 
moved by treating the solution with nickel carbonate or nickel 
hydrate. After adding the boric acid, blue litmus paper is 
strongly reddened, and this acidity due to the boric acid is to 
be maintained in the bath. However, in consequence of the 
use of too large a number of cast anodes, free sulphuric acid 
may form in the bath and this, together with boric acid, can- 
not be recognized by blue litmus paper, since both acids 
redden it. In this case red congo paper, which is not changed 
by boric acid, but is turned blue by sulphuric acid, has to be 
used. If red congo paper is colored blue, it is a sure proof 
that, besides boric acid, free sulphuric acid is present, which 
has to be neutralized for the bath to work in a correct manner. 

The process is again different when a bath prepared with an 
addition of citric acid is to be examined. This organic acid 
colors certain varieties of commercial congo paper blue, just 
like sulphuric acid does, and hence tropaeolin paper has to be 
used, which is not altered by citric acid, but is colored violet 
by free sulphuric acid. 

If a nickel bath has been prepared with the addition of or- 
ganic salts, for instance, sodium citrate, ammonium tartrate or 
others, the formation of free sulphuric acid in the bath cannot 
at first be determined with reagent papers, because the sul- 
phuric acid decomposes the organic salts, neutral sulphates be- 
ing formed, and a quantity of organic acid equivalent to the 
sulphuric acid is liberated. For this reason the content of 
metal in the bath declines, though the presence of sulphuric 
acid cannot be established, because the sulphuric acid formed 



DEPOSITION OF NICKEL AND COBALT. 25 I 

by electrolysis is not consumed for the solution of nickel on the 
anodes, but for the decomposition of the organic salts. 

Now let us suppose the reverse, namely, that in a nickel 
bath prepared with the addition of one of the above mentioned 
acids, free ammonia appears in consequence of the sole use of 
cast anodes, and of the decomposition of ammonium sulphate by 
a strong current. This phenomenon cannot at once be recog- 
nized, because the ammonia is first fixed by the free acid and 
the bath becomes neutral or alkaline only when all the free 
acid which was present has been consumed for fixing the am- 
monia formed. With this process there will generally be con- 
nected an increase in the content of metal, and it will be seen, 
without further explanation, that for the accurate determination 
of the processes and alterations in a nickel bath when in 
operation, the quantitative determination of the free acids, and 
as much as possible, that of the content of metal is required. 

Although it must be said that the busy electroplater will 
frequently not feel inclined to familiarize himself with the 
methods of testing, and seldom have the necessary time for 
executing the determinations of the content of metal, neverthe- 
less the methods will here be described with sufficient detail so 
that those who wish to examine their baths in this respect will 
find the necessary instructions. To be sure, if the electro- 
plater himself is not a practical analytical chemist he will have 
to be taught by some one thoroughly conversant with the sub- 
ject, the management of the analytical balance, how to execute 
the weighings, etc. It is also advisable to procure the stand- 
ard solutions required for volumetric analysis from a reliable 
chemical laboratory, in order to avoid the possibility of arriving 
at incorrect results by the use of inaccurately prepared stand- 
ard solutions. For this reason directions for the preparation 
of standard solutions are omitted, and the methods of examina- 
tion in use for our purposes will now be given. 

The examinations may be made by gravimetric analysis 
(analysis by weight), volumetric analysis (analysis by meas- 
ure), and by electrolytic analysis. The first method is based 



252 ELECTRO-DEPOSITION OF METALS. 

chiefly upon the precipitation in an insoluble form of the con- 
stituent to be determined, and filtering, washing, drying, and 
weighing the precipitate. This method requires considerable 
knowledge of chemistry and analytical skill, and should only 
be resorted to by those not versed in analysis, when other 
more practical methods for the determination of the contents, 
such as volumetric and electrolytic methods, are not known. 

Volumetric analysis is based upon a very different principle 
from that of gravimetric analysis. The constituent to be ascer- 
tained is quantitatively determined by means of a standard 
solution, enough of which is used until the final reaction shows 
that a sufficient quantity has been added. From the known 
content of the standard solution, the constituent to be deter- 
mined is then calculated. This may be explained by an 
example. For instance, the content of sulphuric acid in a 
fluid is to be determined. Measure the quantity of fluid by 
means of a pipette which up to a mark holds exactly 10 cubic 
centimeters. Allow the fluid to run into a clean beaker, dilute 
with about 30 cubic centimeters of water, and heat to about 
122 F. Now, while constantly stirring the fluid in the beaker 
with a glass rod, add standard soda solution from a glass 
burette provided with a glass cork and divided into T V cubic 
centimeters until a piece of congo paper when touched with 
the glass rod is no longer colored blue. The addition of the 
standard soda solution must of course be effected with great 
care. So long as the congo paper shows a vivid blue color, a 
larger quantity may at one time be added, but when the colo- 
ration becomes less vivid, the solution is added drop by drop 
so as to be sure that the last drop is just sufficient to prevent 
the blue coloration which was still perceptible after the addition 
of the previous drop. The drop-test must, of course, be made 
upon a dry portion of the congo paper, which has not been pre- 
viously moistened. When no blue coloration appears after the 
last drop has been added, it is a proof that all the sulphuric 
acid present has been neutralized by the standard soda solution. 
The number and fractions of cubic centimeters consumed are 



DEPOSITION OF NICKEL AND COBALT. 



253 



then read off on the burette, and the quantity of sulphuric acid 
present is calculated as follows : 1 cubic centimeter of standard 
soda solution neutralizes 0.049 gramme of sulphuric acid 
(H 2 SOJ and hence the quantity of sulphuric acid is obtained 
by multiplying the number of cubic centimeters of standard 
soda solution by 0.049. Now, since 10 cubic centimeters were 
measured off by the pipette and titrated, the number found is 
multiplied by 100, which gives the content of sulphuric acid in 
1 liter of the fluid. 

Fig. 128. 




If, for instance, for the neutralization of 10 cubic centimeters 
of the fluid containing sulphuric acid, 5.4 cubic centimeters of 
standard soda solution were required, then the content of sul- 
phuric acid amounts to 5.4x0.049 = 0.2646 gramme, or in 1 
litre to 0.2646 X 100 = 26.46 grammes. 

The electrolytic method of analysis is available only for the 
determination of such metals as can be completely separated 
in a coherent form from their solutions by the current. It is 
based upon the fact that the metallic solution contained in a 



254 ELECTRO-DEPOSITION OF METALS. 

platinum dish is decomposed by the current, and the metal pre- 
cipitated upon the platinum dish. After washing and drying, 
the dish is weighed and the weight of the precipitated metal is 
obtained by deducting the weight of the platinum dish without 
precipitate, which, of course, has been ascertained before 
making the experiment. 

The apparatus generally used for electrolytic analysis is 
shown in Fig. 128. The platinum dish, holding about ^ liter, 
rests upon a metal ring which is secured to the rod of the 
stand, and is in contact with the negative pole of the source of 
current. Into the dish, at a distance of 1 or 2 centimeters 
from the bottom, dips a round platinum disk bent like the bot- 
tom, or a spiral of platinum wire, 1 millimeter thick, which 
serves as anode and is secured by platinum wire in a movable 
support or holder. The latter is carefully insulated from the 
rod of the stand and connected with the positive pole of the 
source of current. During electrolysis the platinum dish is 
covered with a perforated watch-glass to prevent possible loss 
by the evolution of gas. 

Since many precipitates have to be washed without inter- 
rupting the current, it is best to use the washing contrivance 
shown in the illustration to prevent the precipitated metal from 
being redissolved by the electrolyte. With the upper clip 
closed, the shorter leg of the siphon is dipped into the dish. 
The lower clip is then closed and the upper one opened until 
the short leg is filled with water. The upper clip is then 
closed and the lower one opened, whereby the dish is emptied. 
The clip of the longer leg of the siphon is then closed, the 
uppermost clip opened, and the dish filled up to the rim with 
water. The uppermost clip is then closed, the lower one 
opened, and the dish emptied the second time, the operation 
being repeated until the precipitate and dish are thoroughly 
washed. 

Since for complete electrolytic precipitation it is essential to 
operate with correct current-tensions, it is advisable to use an 
accurate current-meter adjusted to 0.05 to 2.5 amperes, as well 
as a voltmeter. 



DEPOSITION OF NICKEL AND COBALT. 255 

The current for electrolysis may be supplied by elements, a 
thermo-electric pile, a dynamo, or an accumulator, but the nec- 
essary regulating resistances must in every case be provided. 

Let us now return to the examination of nickel baths. If by 
qualitative analysis the presence of free sulphuric acid in the 
bath has been established, it can be at once assumed that the 
content of nickel has from the first declined. Hence it will 
scarcely be worth while to determine by volumetric analysis 
the quantity of free sulphuric acid present, and to calculate 
from this the quantity of nickel carbonate or nickel hydrate re- 
quired for neutralization. It will be only necessary to add to 
the bath, stirring constantly, small portions of the nickel salt 
rubbed up with water, until a fresh test with congo paper 
shows no blue coloration. The addition of a small excess of 
nickel carbonate or nickel hydrate is unobjectionable. Besides 
neutralizing the free sulphuric acid, care should at the same 
time be taken to prevent its further formation by increasing 
the number of cast nickel anodes. The case is similar when a 
nickel bath prepared with organic salts, for instance, with 
potassium citrate or sodium citrate, is to be examined. Even 
if it is shown by the reaction that no free sulphuric acid is 
present, the content of nickel, as previously mentioned, may 
have decreased, and the content of free organic acid increased. 
The latter may, however, be neutralized by the addition of 
nickel carbonate or nickel hydrate and, hence, the determina- 
tion of the content of acid by volumetric analysis is not abso- 
lutely necessary. : 

When, on the other hand, a nickel bath has become alkaline, 
the determination of the free alkali by volumetric analysis will 
be of little value, and it will, according to the composition of 
the bath, suffice to neutralize it with dilute sulphuric acid, or 
acidulate it with an organic acid. Since, however, baths 
which have become alkaline possess a higher content of nickel 
than the normal bath, an electrolytic determination of the 
nickel may be of use in order to calculate accurately the 
quantity of water which has to be added to reduce the content 
of nickel to the normal quantity. 



256 ELECTRO-DEPOSITION OF METALS. 

If the bath has been prepared with nickel-ammonium sul- 
phate with additions of ammonium sulphate, or boric acid, or 
if it contains only very small quantities of organic acids, it can 
be directly electrolyzed. 

Bring by means of the pipette exactly 20 cubic centimeters 
of the bath into the platinum dish, add 4 grammes of ammo- 
nium sulphate and 35 to 40 cubic centimeters of ammonia of 
0.96 specific gravity and electrolyze with a current-density = 
0.6 ampere, until no dark coloration appears after adding a 
drop of ammonium sulphate to a few cubic centimeters of the 
electrolyte. Rinse the dish, together with the precipitate, with 
water, remove the water by rinsing with absolute alcohol, rinse 
the dish with pure ether and dry it at 21 2° F. in an air-bath. 
The weight of the precipitate of metallic nickel obtained by 
weighing the platinum dish gives the content of nickel ammo- 
nium sulphate in grammes per liter of bath by multiplying by 
335. From the increase in the content of nickel ammonium 
sulphate shown by the analysis, it can be readily calculated, 
how much water has to be added to the bath to reduce it to 
the original content. 

If a nickel bath contains large quantities of organic acids, 
precipitate 20 cubic centimeters of the bath with sodium sul- 
phide solution, filter and wash the precipitate, dissolve it in 
nitric acid, and evaporate the solution with pure sulphuric acid 
upon the water-bath to drive off the nitric acid. The residue 
is treated as above described. 

2. Deposition oj Cobalt. 

Properties of cobalt. — Cobalt has nearly the same color as 
nickel, with a slightly reddish tinge; its specific gravity is 8.56. 
It is exceedingly hard, highly malleable and ductile, and capa- 
ble of taking a polish. It is slightly magnetic, and preserves 
this property even when alloyed with mercury. It is rapidly 
dissolved by nitric acid, and slowly by dilute sulphuric and 
hydrochloric acids. 

For plating with cobalt, the baths given under nickeling may 



DEPOSITION OF NICKEL AND COBALT. 257 

be used by substituting for the nickel salt a corresponding 
quantity of cobalt salt. By observing the rules given for nickel- 
ing, the operation proceeds with ease. Anodes of metallic 
cobalt are to be used in place of nickel anodes. 

Nickel being cheaper and its color somewhat whiter, electro- 
plating with cobalt is but little practiced. On account of the 
greater solubility of cobalt in dilute sulphuric acid it is, how- 
ever, under all circumstances, to be preferred for facing valuable 
copper plates for printing. 

According to the more or less careful adjustment of such 
plates in the press, many places of the facing are more or less 
attacked, and it may be desired to remove the coating and 
make a fresh deposit. For this purpose, GaifTe has proposed 
the use of cobalt in place of nickel, because the former dis- 
solves slowly but completely in dilute sulphuric acid. He 
recommends a solution of 1 part of chloride of cobalt in 16 of 
water. The solution is to be neutralized with aqua ammonia, 
and the plates are to be electro- plated with the use of a mod- 
erate current. 

Cobalt precipitated from its chloride solution, however, does 
not yield a hard coating, and hence the following bath is 
recommended for the purpose: Double sulphate of cobalt and 
ammonium 21 ozs., cobaltous carbonate 0.8 oz., crystallized 
boric acid 10^ ozs., water 10 quarts. 

The bath is prepared in the same manner as No. VII., given 
under "Nickeling." It requires a tension of 2.5 to 2.75 volts; 
current-density, 0.6 ampere. 

To determine whether copper, and how much of it, is dissolved 
in stripping the cobalt deposit from cobalted copper plates, a 
copper plate with a surface of 7^ square inches was coated with 
7.71 grains of cobalt and placed in dilute sulphuric acid (1 part 
acid of 66° Be., to 12.5 parts of water). After the acid had acted 
for 16 hours, the cobalt deposit was partially dissolved and had 
partially collected in lamina upon the bottom of the vessel, the 
copper plate being entirely freed. On weighing the copper plate 
it was shown that it had lost about 0.0063 P er cent., this loss 
17 



258 ELECTRO-DEPOSITION OF METALS. 

being apparently chiefly from the back of the plate, the engraved 
side exhibiting no trace of corrosion. This experiment proved 
that there is no danger of destroying the copper plate by strip- 
ping the cobalt deposit with dilute sulphuric acid, provided the 
operation is executed with due care and attention. 

W^arren has described a cobalt solution which can be de- 
composed in a single cell apparatus, and for this reason would 
seem suitable for electro-plating small articles en masse. For 
the preparation of this bath, dissolve 3*/£ ounces of chloride of 
cobalt in as little water as possible, and compound the solution 
with concentrated solution of Rochelle salt until the voluminous 
precipitate at first formed, is almost entirely redissolved, and 
then filter. Bring the bath into a vessel and place the latter in 
a clay cell filled with concentrated solution of sal ammoniac or 
of common salt, and containing a zinc cylinder. Connect the 
objects to be plated to the zinc by a copper wire and allow 
them to dip in the cobalt solution. With a closed circuit the 
objects become gradually coated with a lustrous cobalt deposit 
which, after 2 hours, is sufficiently heavy to bear vigorous 
polishing with the bob. Zinc may be coated in the same 
manner. 

The following solution has been recommended by Mr. G. W. 
Beardslee, of Brooklyn, N. Y., and is claimed to yield a good 
deposit of cobalt which is very white, exceedingly hard, and 
tenaciously adherent : Dissolve pure cobalt in boiling hydro- 
chloric acid and evaporate the solution to dryness. Next dis- 
solve 4 to 6 ozs. of the resulting salt in 1 gallon of distilled 
water, to which add liquid ammonia until it turns red litmus- 
paper blue. The solution being thus rendered slightly alka- 
line, is ready for use. A battery power of from two to five 
Smee cells will be sufficient to do good work. Care must be 
had not to allow the solution to lose its slightly alkaline con- 
dition, upon which the whiteness, uniformity of deposit, and its 
adhesion to the basis- metal greatly depend. 

For cobalting small fancy articles of copper, brass, or steel, 
R. Daub recommends the following bath: Dissolve 4^ ozs. of 



DEPOSITION OF NICKEL AND COBALT. 259 

double sulphate of cobalt and ammonium in 4^ quarts of 
water. The solution should show, at 59 F., a specific gravity 
of 1. 01 5. The most suitable current-strength is 0.8 ampere 
with about two volts. The size of the anodes is of great influ- 
ence as regards the uniformity of the cobalting. For the 
deposition of cobalt upon brass, copper, steel, or iron, the 
anodes may consist of rolled cobalt in strips about 2 inches 
wide and 10 to 12 inches long, according to the size of the 
articles. The anodes are arranged on the sides of the vat, 
about 6 inches apart. With the use of a large vat — holding 
from 500 to 1000 quarts of bath — a corresponding series of 
such anodes are to be suspended to a conducting rod which 
rests lengthwise upon the ends of the vat. The metallic arti- 
cles should be coated with a thin film of cobalt in a few seconds 
after having been suspended in the bath, and the current- 
strength is then reduced, to be increased only when more 
articles are brought into the bath. The mode of treatment is 
different from that in the nickel bath, and, since cobalt deposits 
with greater ease than nickel, the regulation of the current is 
the principal point. The current- strength should be reduced 
as soon as the articles are entirely and nicely coated with 
cobalt. Copper articles require at the beginning a stronger 
current than brass objects, while for articles of iron or steel the 
current should be weaker than for either brass or copper. 
Places in relief should be kept as far as possible from the 
anodes to prevent blackening or burning. According to 
R. Daub, the principal condition for the success of the opera- 
tion is to maintain a uniform density of the bath, either by the 
addition of water or of cobalt salt, as may be required. The 
color of the deposit is much influenced by the current-strength., 
Thus a deposit with 1 volt and a large anode-surface is not so 
white as one with two volts and a smaller anode-surface, about 
2 /?> of that of the cathode. Cast-brass is especially suitable for 
cobalting, as well as metallic articles which are kept in dry 
rooms or used for ornamental purposes. 

Cobalting by contact. — While nickeling by contact with zinc 



260 ELECTRO-DEPOSITION OF METALS. 

yields only incomplete results, the cobalting of copper and brass 
articles succeeds very well with the use of the following bath : 
Crystallized cobalt sulphate 0.35 oz., crystallized sal ammoniac 
0.07 oz., water 1 quart. Heat the bath to between 104 and 
122° F., and immerse the previously cleansed and pickled arti- 
cles in the bath, bringing them in contact with a bright zinc 
surface not too small ; for small articles a zinc sieve may be used. 
In 3 or 4 minutes the coating is heavy enough to bear vigorous 
polishing. 



CHAPTER VIII. 

DEPOSITION OF COPPER, BRASS AND BRONZE. 

i. Deposition of Copper. 

Properties of copper. — Copper has a characteristic red color, 
and possesses strong lustre. It is very tenacious, may be rolled 
to thin lamina, and readily drawn into fine wire. The specific 
gravity of wrought copper is 8.95, and of cast 8.92. Copper 
fuses more readily than gold, but with greater difficulty than 
silver. 

In a humid atmosphere containing carbonic acid, copper 
becomes gradually coated with a green deposit of basic carbon- 
ate. When slightly heated it acquires a red coating of cuprous 
oxide, and when strongly heated a black coating of cupric oxide 
with some cuprous oxide. Copper is most readily attacked by 
nitric acid, but is slowly dissolved when immersed in heated 
hydrochloric or sulphuric acid. With exclusion of the air, it is 
not dissolved by dilute sulphuric or hydrochloric acid> and but 
slightly with admission of the air. Liquid ammonia causes a 
rapid oxidation of copper in the air and the formation of a blue 
solution. An excess of potassium cyanide dissolves copper. 
Sulphuretted hydrogen blackens bright copper. 

Copper baths. — The composition of these baths depends on 
the purpose they are to serve, and below are mentioned the 
most approved baths, with the exception of the acid copper 
bath used for plastic deposits of copper, which will be dis- 
cussed later on under " Copper galvanoplasty." 

In most cases the more electro- positive metals, zinc, iron, tin, 
etc., are to be coppered either as preparation for the succeed- 
ing process of nickeling, silvering, or gilding, or to protect 
them against oxidation, or for the purpose of decoration. The 

(261) 



262 ELECTRO-DEPOSITION OF METALS. 

above-mentioned electro-positive metals, however, decompose 
acid copper solutions and separate from them pulverulent cop- 
per, while an equivalent portion of zinc, iron, tin, etc., is dis- 
solved. For this reason, such solutions cannot be used for 
coating these metals, and alkaline copper baths are exclusively 
employed, which may be arranged under two groups — those 
containing potassium cyanide, and those without it. 

Hassauer prepares a copper bath by dissolving ^>% ozs. of 
copper cyanide in a solution of \J}& ozs. of 70 per cent, 
potassium cyanide in 3 quarts of water, boiling, filtering, and 
diluting with 7 quarts of water to a 10-quart bath. This bath 
works very well when heated to between 113 and 122 F., 
but when used cold requires a very strong current, and hence 
the use of the following formulae is recommended: — 

Copper baths for iron and steel articles. — I. To be used at the 
ordinary temperature . — Water 10 quarts, bisulphite of soda in 
powder 7 ozs., crystallized carbonate of soda 14 ozs., neutral 
acetate of copper 7 ozs., 75 per cent, potassium cyanide 7 ozs., 
spirits of sal ammoniac 4.4 ozs. 

II. For hot coppering {at between 14.0° and 158° F.). Rose- 
leur recommends: Water 10 quarts, bisulphite of soda in 
powder 2^ ozs., crystallized carbonate of soda 7 ozs., neutral 
acetate of copper 7 ozs., 75 per cent, cyanide of potassium 
9^ ozs., spirit of sal ammoniac 4 ozs. 

The baths are best prepared as follows : Dissolve the bisul- 
phite and carbonate of soda in one-half of the water, the 
potassium cyanide in the other half, and mix the copper salt 
with the spirit of sal ammoniac ; then pour the blue ammoniacal 
copper solution into the solution of the soda salts, and finally 
add the potassium cyanide solution; the bath will then be clear 
and colorless. Boiling, though not absolutely necessary, is of 
advantage, after which the solution is to be filtered. 

According to thorough investigations made, the excess of 
carbonate of soda in formula I. serves no special purpose, but 
on the contrary, in many cases, is directly detrimental ; neither 
is the use of ammonia of any special advantage, and it may just 



DEPOSITION OF COPPER, BRASS AND BRONZE. 263 

as well, or rather better, be omitted. Further, the use of sepa- 
rate baths for cold and warm coppering is at least questionable. 
It is believed that a single bath suffices for both cases, heating 
having been found of special advantage only for rapid and 
thick coppering, or for obtaining particular shades which are 
produced with difficulty in the cold bath, but without trouble 
in the heated bath. 

The following formula may be highly recommended, a cop- 
per bath composed according to it always yielding good and 
sure results : — 

III. Water 10 quarts, crystallized carbonate of coda 8j^ ozs., 
crystallized bisulphite of soda 7 ozs., neutral acetate of copper 
7 ozs., 98 or 99 per cent, potassium cyanide 8^ ozs. 

The bath is prepared as follows : Dissolve in 7 quarts of 
warm water the carbonate of soda, gradually add the bisulphite 
of soda to prevent violent effervescence, and then add, with 
vigorous stirring, the acetate of copper in small portions. 
Dissolve the potassium cyanide in 3 quarts of cold water, and 
mix both solutions when the first is cold. By thorough stirring 
with a clean wooden stick a clear solution is quickly obtained 
which is allowed to settle and siphoned off clear. If after the 
addition of the potassium cyanide the bath should not become 
colorless, or at least wine-yellow, add a small quantity more of 
potassium cyanide. This bath does not require a strong cur- 
rent, and yields an especially heavy coppering of a beautiful 
red color. A current of 0.4 ampere at a tension of 3 to 3.5 
volts is calculated for 15 J^ square inches of surface of objects. 
With a greater content of potassium cyanide the tension may 
be correspondingly decreased. 

For coppering zinc articles > Roseleur recommends the fol- 
lowing bath : — 

IV. Water 10 quarts, tartar, free from lime, 6.J ozs., crystal- 
lized carbonate of soda 15 ozs., blue vitriol 6.7 ozs., caustic 
soda lye of 16 Be. ^ lb. 

To prepare this bath, dissolve the tartar and the crystallized 
carbonate of soda in % of the water, and the blue vitriol in the 



264 ELECTRO-DEPOSITION OF METALS. 

remaining %, and mix both solutions. Filter off the precipi- 
tate, dissolve it in the caustic soda lye, and add this solution to 
the other. 

This bath works very well, and may be recommended to 
electro-platers who copper zinc exclusively ; but where all kinds 
of metals are to be coppered, bath No. III. is to be preferred, 
it yielding equally good results for zinc. 

For small zinc objects which are to be coppered in a sieve, 
bath No. III. is used, it being heated for this purpose, and a 
little more potassium cyanide added. Roseleur recommends 
for the same purpose a bath composed as follows : — 

V. Water 10 quarts, neutral crystallized bisulphite of soda 
i^ozs., neutral acetate of copper 8 ozs., 75 per cent, potass- 
ium cyanide i2j^ ozs., and ammonia y 2 oz. The bath is pre- 
pared in the same manner as formulae I. to III. 

In preparing copper baths, the acetate of copper prescribed 
in the preceding formulae may be replaced by the carbonate or 
sulphate, the substitution of the latter, after its previous con- 
version into carbonate, being of special advantage in order not 
to impart to the bath too great a resistance by the potassium 
sulphate, formed by reciprocal decomposition. The following 
formula is especially suitable for the use of sulphate of copper 
(blue vitriol) : — 

VI. Blue vitriol ioj4 ozs. 

Crystallized carbonate of soda . . 10^ " 



Water . . . . . . .10 quarts. 

Pulverized bisulphite of soda ... 7 ozs. 

Crystallized carbonate of soda . . 8}£ ozs. 

98 to 99 per cent, potassium cyanide . 8^ " 
First dissolve the 10^ ozs. of blue vitriol and the 10^ ozs. 
of crystallized carbonate of soda, each by itself, in hot water, 
and mix the two solutions. Allow the precipitate of carbonate 
of copper to settle, and pour off the supernatant clear fluid. 
Then pour upon the precipitate 5 quarts of water, add the 
bisulphite of soda, next the carbonate of soda, and mix this 



DEPOSITION OF COPPER, BRASS AND BRONZE. 265 

solution with the solution of the potassium cyanide in 5 quarts 
of water. The fluid rapidly becomes clear and colorless, when 
it is boiled and filtered. 

In a recent formula cuprous oxide, which is found in com- 
merce under the name of cupron, is used in place of cupric 
oxide. 

VII. Cupron 3^ ozs., 99 per cent, potassium cyanide 10 j4 
ozs., pulverized sodium bisulphite 10^ ozs., water 15 quarts. 

Dissolve the potassium cyanide in one-half the prescribed 
quantity of water (cold), then gradually stir in the cupron, 
and after the solution of the latter, add the sodium bisulphite 
previously dissolved in the other half of the water. 

In place of cupron, copper sulphite may be used. This salt 
dissolves in potassium cyanide without perceptible evolution of 
cyanogen, since it contains more than the sufficient quantity of 
sulphurous acid required for the reduction of the oxide salt 
present. 

Suitable formulae for baths with copper sulphite are as 
follows : 

VIII. Ammonia-soda if ozs., 99 per cent, potassium 
cyanide S}4 ozs., copper sulphite 4^ ozs., water 10 quarts; or, 

IX. 60 per cent, potassium cyanide 14 ozs., copper sulphite 
4j£ ozs., water 10 quarts. 

Dissolve the salts in the order given in 5 quarts of the water, 
stirring constantly, and then add the remaining 5 quarts of 
water. 

The deposits obtained in these baths are of a beautiful warm 
color, very adherent and dense. 

A bath recently recommended by the " Metallarbeiter " con- 
sists of potassium copper cyanide 2^ ozs., 99 per cent, potas- 
sium cyanide 1.12 drachms, crystallized sal ammoniac 1.12 
drachms, ammonia-soda j£ oz., water 1 quart. With the ex- 
ception of easy preparation by simply dissolving the salts, this 
bath has no advantage. It possesses, however, the disad- 
vantage of all baths containing sal ammoniac when iron is the 
basis-metal, as has been already explained under "Nickeling." 



266 ELECfRO-DEPOSITION OF METALS. 

According to the directions given the bath must be operated at 
68° to 75° F., very likely for the reason that for want of suffi- 
cient and suitable conducting salts, the resistance at the ordinary 
temperature is quite great. However, the warming of the bath 
is another disadvantage. 

Of the many directions for copper baths without potassium 
cyanide, to which also belongs the bath prepared according to 
formula IV., and which have chiefly been proposed for copper- 
ing cast and wrought iron, only a few heed be mentioned as 
being actually available. 

Weil obtains a deposit of copper in a bath consisting of a 
solution of blue vftriol in an alkaline solution of tartrate of 
potassium or sodium. Such a bath is composed as follows: — 

X. Water io quarts, potassium sodium tartrate (Rochelle 
salt) 53 ozs., blue vitriol io^ ozs., 6o per cent, caustic soda 
28 ozs. 

The chief purpose of the large content of caustic soda is to 
keep the tartrate of copper, which is almost insoluble in water, 
in solution. According to Weil, the coppering may be exe- 
cuted in three different ways, as follows: — 

The iron articles tied to zinc wires or in contact with zinc 
strips are brought into the bath ; the coppering thus taking 
place by contact. Or, porous clay cells are placed in the bath 
containing the articles , these clay cells are filled with soda lye 
in which zinc plates connected with the object-rods are allowed 
to dip, the arrangement in this case forming an element with 
which, by the solution of the zinc in the soda lye, a current is 
produced, which effects the decomposition of the copper solu- 
tion and the deposition. When saturated with zinc the soda 
lye becomes ineffective, and, according to Weil, it may be re- 
generated by the addition of sodium sulphide, which separates 
the dissolved zinc as zinc sulphide. The third method of copper- 
ing consists in the use of the current of a battery or of a dynamo- 
machine, in which case copper anodes have, of course, to be 
employed. 

A copper bath recommended by Walenn is composed of a 



DEPOSITION OF COPPER, BRASS AND BRONZE. 267 

solution of equal parts of tartrate of ammonia and potassium 
cyanide, in which 3 to 5 per cent, of copper (in the form of 
blue vitriol or moist cupric hydrate) is dissolved. The bath is 
to be heated to about 140 F. 

Copper bath according to Pfanhauser. — Dissolve 2j^ ozs. of 
cyanide of copper, ij4 drachms each of pure ioo per cent, 
potassium cyanide and crystallized sal ammoniac, and 5^ 
drachms of ammonia soda in 1 quart of lukewarm water, stir- 
ring constantly until all the salts are dissolved. 

The temperature of the bath should be between 68° and JJ° 
F., and the strength of current 3 volts. Density of current 0.5 
ampere. In case the bath should become poor in metal, cyan- 
ide of copper has to be added. When the copper anodes be- 
come coated with too great an abundance of green slime, which 
does not decrease during the night when the bath is not work- 
ing, some potassium cyanide, about % drachm per quart, 
should be added. 

Ganduiris copper bath consists of a solution of oxalate of 
copper with oxalate of ammonia and free oxalic acid. Fon- 
taine asserts that the bath works well, when heated to between 
140 and 150 F. 

Copper baths containing cyanide cannot be brought into 
pitched vats, vats of stoneware or enameled iron being used for 
smaller baths, and for larger, basins of brick set in cement, or 
iron reservoirs lined with ebonite. For large baths containing 
potassium cyanide wooden vats lined with lead can be used 
without disadvantage, since a slight coating of cyanide of lead, 
which may be formed upon the lead, is insoluble in potassium 
cyanide, and even if a small quantity of cyanide of lead would 
be dissolved in the bath by the presence of organic acids, a 
separation of lead besides copper upon the cathodes does not 
take place. 

Execution of copper-plating. — The general rules given under 
nickeling, as regards the suitable composition of the bath, 
correct selection of anodes, careful scouring and pickling of the 
objects and proper current-strength also apply to copper- 
plating. 



268 ELECTRO-DEPOSITION OF METALS. 

Annealed sheets of pure copper with as large a surface as 
possible serve as anodes. In all baths containing cyanide the 
anodes become, in a comparatively short time, coated with a 
greenish slime consisting of a basic copper cyanide mostly 
soluble in excess of potassium cyanide. When a very thick 
formation of such slime takes place, potassium cyanide is 
wanting, and has to be added. Other phenomena appearing 
in copper baths containing cyanide may as well here be men- 
tioned. Too large an excess of potassium cyanide causes a 
strong evolution of hydrogen bubbles on the objects ; but no 
deposition of copper, or only a slight one, takes place, which 
besides has the tendency to peel off. If this phenomenon ap- 
pears after adding potassium cyanide, the excess can be readily 
removed by the addition of copper salt, best cyanide of cop- 
per, stirred with a small quantity of the bath to a thinly fluid 
paste and added to the bath with constant and long-continued 
stirring. After each addition, a test is made whether an object 
suspended in the bath is rapidly and regularly coppered ; if 
such is not the case, the addition of cyanide of copper is re- 
peated until the bath works in a faultless and correct manner. 
On the other hand, a deposit may not be formed for the want 
of potassium cyanide, which is already indicated by a thick 
formation of slime on the anodes, and by the fluid acquiring a 
pale blue color ; or the metallic content of the bath may be too 
small. While in the first case a slight addition of potassium 
cyanide alone will cause the bath to work correctly, in the 
other case, an addition of solution of copper cyanide in potas- 
sium cyanide is required to augment the content of metal in 
the bath, it being best to introduce together with the metallic 
cyanide solution a small quantity of carbonate and bisulphite 
of soda, in order to decrease the resistance to conductivity. 
In place of solution of copper cyanide in potassium cyanide, 
commercial crystallized potassium copper cyanide may be 
used. In plating with a strong current the anodes become 
frequently coated to such an extent that finally no current 
passes into the bath, the excess of potassium cyanide being 



DEPOSITION OF COPPER, BRASS AND BRONZE. 269 

unable to dissolve the copper cyanide as rapidly as it is formed. 
In this case scouring the anodes is the only remedy. 

Many platers are of the opinion that the articles to be copper- 
plated do not require very careful cleaning and pickling before 
plating because this is sufficiently effected by the baths them- 
selves, by those containing potassium cyanide, as well as by 
those with alkaline-organic combinations. This opinion, how- 
ever, is wrong. It is true the potassium cyanide dissolves a 
layer of oxide, but not, or at least very incompletely, any grease 
present upon the articles, and hence it is advisable to free 
articles intended for coppering as thoroughly from grease as 
articles to be nickeled. 

The preliminary scouring and pickling of the articles to be 
coppered are executed according to the directions given on p. 
163. The same precautions referred to under "Nickeling" 
have to be used in suspending the objects in the bath, and the 
directions given there for the suitable arrangement of the 
anodes, etc., also apply to coppering. However, as a copper 
bath conducts better than a nickel bath, the distance between 
the anodes and the objects may, if necessary, be somewhat 
greater. 

With a proper arrangement of the anodes and correct regu- 
lation of the current, the objects should be entirely coated with 
copper in a few minutes after being suspended in the bath. In 
five to ten minutes the objects are taken from the bath and 
brushed with a scratch-brush of not too hard brass wires, 
whereby the deposit should everywhere show itself to be dur- 
able and adherent. Defective places are especially thoroughly 
scratch-brushed, scoured, and pickled ; the objects are then 
returned to the bath. For solid and heavy plating the objects 
remain in the bath until the original lustre and red tone 
of the coppering disappear and pass into a dull discolored 
brown. At this stage the objects are again scratch-brushed 
until they show lustre and the red copper color, whereby it is 
of advantage to moisten them with tartar water. They are 
then again returned to the bath, where they remain until the 



27O ELECTRO-DEPOSITION OF METALS. 

dull discolored tone reappears. They are then taken out, 
scratch-brushed bright, rinsed in several clean waters, plunged 
into hot water, and finally dried, first in sawdust and then 
thoroughly, at a high temperature, in the drying chamber. 
Special attention must be paid to the thorough washing of the 
coppered objects, because, if anything of the bath containing 
cyanide remains in the depressions or pores, small, dark y round 
stains appear on those places, which cannot be removed, or at 
least only with great difficulty, they reappearing again in a 
short time after having been apparently removed. This forma- 
tion of stains appears especially frequently upon coppered (as 
well as brassed) iron and zinc castings, which cannot be pro- 
duced without pores. To prevent the formation of these stains 
the following method is recommended : Since the rinsing in 
many waters, and even allowing the objects to lie for hours in 
running water, offer no guarantee that every trace of fluid con- 
taining cyanide has been removed, the objects are brought into 
a slightly acid bath which decomposes the fluid, a mixture of I 
part of acetic acid and 50 parts of water being well adapted for 
the purpose. The objects are allowed to remain in this mix- 
ture for three to five minutes, when they are rinsed off in water 
and dipped for a few minutes in dilute milk of lime. They are 
finally rinsed off and dried. Coppered castings thus treated 
will show no stains. 

O. Shultz obtained a patent for the following method for re- 
moving the hydrochloric acid from the pores, and thus prevent- 
ing the formation of stains: The plated objects are placed in a 
room which can be hermetically closed. The air is then re- 
moved from the room by the introduction of steam of a high 
tension, and by means of an air-pump, and water sprinkled 
upon the objects. By this treatment in vacuum the fluid in the 
pores comes to the surface, and the salt solution is removed by 
the water sprinkled over the articles. 

After drying, the deposit of copper, if it is to show high 
lustre, is polished with soft wheels of fine flannel and dry Vienna 
lime. Commercial rouge FFF, moistened with a little alcohol, 



DEPOSITION OF COPPER, BRASS AND BRONZE. 2JI 

is also an excellent polishing agent for copper and all other 
soft metals. 

As is well known, massive copper rapidly oxidizes in a 
humid atmosphere, and this is the case to a still greater extent 
with electro -deposited copper. Hence, the coppered objects, 
if they are not to be further coated with a non-oxidizing metal, 
have to be provided with a colorless, transparent coat of lac- 
quer (see "Lacquering"). 

It frequent happens that slightly coppered (as well as 
slightly brassed) objects, especially of zinc, after some time, be- 
come entirely white and show no trace of the deposit. This is 
due to the deposit penetrating into the basis-metal, as already 
explained. Lacquering in this case is of no avail, the deposit 
also disappearing under the-coatjqf lacquer. The only remedy 
against this phenomenon is a heavier deposit. , 

If the coppered objects are to be coated with another metal, 
drying is omitted, and after careful rinsing they are directly 
brought into the respective bath, or into the quicking pickle, if, 
as, for instance, in silvering, quicking has to be done. In such 
cases, where the copper deposit serves only as an intermediary 
for the reception of another metallic coating, the objects need 
not to be coppered as thickly, as previously described, by 
treating them three times in the bath. Preliminary coppering 
for 5 to 10 minutes suffices in all cases, which is succeeded by 
scratch-brushing in order to be convinced that the deposit 
adheres firmly and that the basis-metal is uniformly coated. 
The objects are then suspended in the bath for 5 to 10 minutes 
longer with a weak current. 

In coppering sheet iron or sheet zinc which is to be nickeled, the 
sheets are taken from the bath after 3 to 5 minutes, at any rate 
while they still retain lustre, scratch-brushing being in this case 
omitted. For coppering such sheets a current-density of 0.5 
ampere with a tension of 3.5 to 4 volts is required. 

The treatment of copper baths when they become inactive 
and other abnormal phenomena have already been referred to. 
All other rules for electro-plating baths given in Chapter VL 
must here also be observed. 



272 ELECTRO DEPOSITION OF METALS. 

For coppering small articles en masse in sieves, it is recom- 
mended to have the copper baths quite hot ; for the rest, the 
process is the same as that given for nickeling small articles en 
masse. 

Coppering by contact and dipping. — According to LudersdorfT, 
a solution of tartrate of copper in neutral potassium tartrate 
serves for this purpose. A suitable modification of this bath is 
as follows: Heat 10 quarts of water to 140 F., add 2 lbs. of 
pulverized tartar (cream of tartar) free from lime, and ioj^ ozs. 
of carbonate of copper. Keep the fluid at the temperature 
above mentioned until the evolution of gas due to the decom- 
position of the carbonate of copper ceases, and then add in 
small portions, and with constant stirring, pure whiting until 
effervescence is no longer perceptible. Filter off the fluid from 
the tartrate of lime, separate and wash the precipitate, so that 
the filtrate, inclusive of the wash water, amounts to 10 or 12 
quarts. 

Zinc is coppered in this bath by simple immersion ; other 
metals have to be brought in contact with zinc. 

To coat zinc plates with a very thin but hard layer of copper, 
immerse the plates in a bath composed of 100 parts of water 
saturated with cupric chloride — cupric chloride 40 parts, water 
60 — 150 parts of ammonia and 3000 parts of water. For very- 
solid coppering, the above-described bath, which is of a beauti- 
ful blue color, is used, and a saturated solution of potassium 
cyanide in water added until the blue of the first mixture has 
quite disappeared. For plates engraved with the burin or for 
stamped plates, it is best to use a mixture of cyanide of copper 
with neutral potassium sulphate, to which is added a mixture of 
a saturated solution of blue vitriol in water and of water satur- 
ated with cyanide of copper. The bath is ready for use when 
the precipitate is completely dissolved and the fluid entirely 
discolored. 

Another contact coppering bath is that prepared according 
to formula X., proposed by Weil. In this bath zinc is also 
coppered by simple immersion, and copper and iron in con- 
tact with zinc strips. 



DEPOSITION OF COPPER, BRASS AND BRONZE. 273 

. According to Bacco, a copper bath in which zinc may be 
coppered by immersion, and iron and other metals in contact 
with zinc, is prepared by adding to a saturated solution of blue 
vitriol, potassium cyanide solution until the precipitate of 
cyanide of copper which is formed is again dissolved. Then 
add ^ to \ of the volume of liquid ammonia and dilute with 
water to 8° Be. 

The so-called brush-coppering, which has been recommended, 
may here be mentioned. This process may be of practical 
advantage for coppering very large objects which by another 
method could only be coated with difficulty. The deposit 
of copper is, of course, very thin. The process is executed 
as follows : The utensils required are two vessels of sufficient 
size, each provided with a brush, preferably so wide that the 
entire surface of the object to be treated can be coated with 
one application. One of the vessels contains a strongly satu- 
rated solution of caustic soda, and the other a strongly satu- 
rated solution of blue vitriol. For coppering, the well-cleansed 
object is first uniformly coated with a brushful of the caustic 
soda solution, and then also with a brushful of the blue vitriol 
solution. A quite thick film of copper is immediately deposited 
upon the object. Care must be had not to have the brush too 
full, and not to touch the places once gone over the second 
time, as otherwise the layer of copper does not adhere firmly. 

Many iron and steel objects are provided with a thin film of 
copper in order to give them a more pleasing appearance. For 
this purpose a copper solution of 10 quarts of water, 1 ^ ozs. of 
blue vitriol, and 1^ ozs. of pure concentrated sulphuric acid 
may be used. Dip the iron or steel objects, previously freed 
from grease and oxide, for a moment in the solution, moving 
them constantly to and fro ; then rinse them immediately in 
ample water, and dry. By keeping the articles too long in the 
solution the copper separates in a pulverulent form, and does 
not adhere. 

Steel pens, needles' eyes, etc., may be coppered by diluting 
the copper solution just mentioned with double the quantity of 
18 



274 ELECTRO-DEPOSITION O* METALS. 

water, moistening sawdust with the solution and revolving the 
latter, together with the articles to be coppered, in a wooden 
tumbling barrel (p. 139). 

The i7ilaying of depressions of coppered art-castings with 
black may be done in different ways. Some blacken the ground 
by applying a mixture of spirit lacquer with lampblack and 
graphite, while others use oil of turpentine with lampblack and 
a few drops of copal lacquer. A very thin nigrosin lacquer 
mixed with finely pulverized graphite is very suitable for the 
purpose. When the lacquer is dry the elevated places which 
are to show the copper color are cleansed with a linen rag 
moistened with alcohol. 

Electrolytically coppered articles may be inlaid black by 
coating them, after thorough scouring and pickling, with 
arsenic in one of the baths given under " Electro-deposition of 
Arsenic," and, after drying in hot water and sawdust, freeing 
the surfaces and profiles, which are to appear coppered, from 
the coating of arsenic by polishing upon a felt wheel. If this 
polishing is to be avoided, the portions which are not to be 
black may be coated with stopping-off varnish, and arsenic 
deposited upon the places left free. 

For coloring, platinizing, and oxidizing of copper, see the 
proper chapter. 

Examination of Copper-baths Containing Potassium Cyanide. 

In the preceding sections several characteristic indications 
which serve for the qualitative examination of these baths have 
already been given. Like all baths containing potassium 
cyanide, their original composition gradually suffers extensive 
alterations by the decomposition of the potassium cyanide, 
which by the carbonic acid of the air is changed to potassium 
carbonate and hydrogen cyanide, and spontaneously also to 
ammonia and potassium formate. The potassium cyanide is 
also split up by the current, potassium hydroxide being 
formed, together with decomposition of water, which by the 
carbonic acid of the air is gradually converted into potash, 



DEPOSITION OF COPPER, BRASS AND BRONZE. 275 

while hydrogen cyanide and hydrogen escape. Under certain 
conditions an oxidation of the potassium cyanide to potassium 
cyanate also takes place. 

The excess of potassium cyanide required for the correct 
performance of the copper-bath is therefore gradually con- 
sumed, and the bath, at first of a wine-yellow color, acquires a 
blue coloration, and does no longer yield a good deposit. 
When such is the case the same quantity of copper which is 
withdrawn from the bath by the deposit, is not dissolved from 
the anodes and, hence, the determination of the content of free 
potassium cyanide as well, as that of the content of copper, may 
at times be necessary. A determination of the potassium car- 
bonate (potash) formed in the bath and its removal, or con- 
version into potassium cyanide by the addition of the corre- 
sponding quantity of barium cyanide solution, which will be 
referred to under silver baths, cannot be recommended, be- 
cause this determination in copper baths which contain, as is 
generally the case, sulphides, is troublesome, and because an 
accumulation of potash in copper baths does not produce the 
same evils as in a silver bath. If, however, a copper bath, after 
working for years, has become thick in consequence of a large 
content of potash, it can be renewed without considerable ex- 
pense, or, if this is not desired, it can be regenerated by dilut- 
ing with water and increasing the content of copper and of 
potassium cyanide. 

Hence, the determination of the free potassium cyanide 
(*. e. } not fixed on copper), and that of the copper will here 
only be discussed. 

Determination of potassium cyanide. — The best and most 
rapid method for this purpose is by titrating with decinormal 
solution of silver nitrate. Silver nitrate and potassium cyanide 
form finally potassium nitrate and insoluble silver cyanide, the 
latter, however, being redissolved to potassium silver cyanide 
so long as free potassium cyanide is present. Since potassium 
silver cyanide contains two molecules of cyanogen, one mole- 
cule of silver nitrate corresponds to two molecules of potassium 



276 ELECTRO-DEPOSITION OF METALS. 

cyanide and 1 cubic centimeter of decinormal solution of silver 
nitrate corresponds to 0.013 gramme of potassium cyanide. 

Bring, by means of a pipette, 5 cubic centimeters of the 
copper bath into a beaker having a capacity of about % liter 
Dilute with about 150 cubic centimeters of water, add one or 
two drops of saturated common salt solution, and then, whilst 
constantly stirring the fluid in the beaker, allow to flow in from 
the burette silver nitrate solution so long as the precipitate 
formed dissolves rapidly. 

When solution becomes sluggish add, stirring constantly, 
silver nitrate solution drop by drop, waiting after the addition 
of each drop until the fluid has again become clear. When 
the fluid does not become clear after adding the last drop, and 
it shows a slight turbidity, no more free potassium cyanide is 
present. By multiplying the cubic centimeters of decinormal 
solution of silver nitrate used by 2.6, the content of potassium 
cyanide per liter of bath is found. 

Suppose for 5 cubic centimeters of bath, 8.2 cubic centi- 
meters of silver solution have been used, then one liter of the 
bath contains 8.2 x 2.6= 21.32 grammes of free potassium 
cyanide, because 1 cubic centimeter of silver solution corre- 
sponds to 0.013 gramme of potassium cyanide, therefore, 8.2 
cubic centimeters = 8.2. 0.013 = 0.1066 grammes, from 
which results by calculation 

5 : 0.1066= IOOO: x 
x = 21.32 grammes. 

If now the initial content of free potassium cyanide in the 
freshly-prepared bath had been determined, a later determina- 
tion will show the deficiency of it which has taken place. It 
must, however, be taken into consideration that the potassium 
formate formed by the decomposition of the potassium cyanide 
may, up to a certain degree, apparently fill the role of the 
potassium cyanide, in so far as it decreases the conducting re- 
sistance of the bath, but it does not contribute to the solution 
of the anodes. Hence, if the established deficiency of potas- 
sium cyanide would be replaced by equally large quantities of 



DEPOSITION OF COPPER, BRASS AND BRONZE. 277 

the salt, there would be danger of too much of it getting into 
the bath, and the latter would conduct too readily, which would 
result in the deposit precipitating too rapidly and turning out 
less adherent. 

Hence, it is evident that analytical methods alone are not 
sufficient for maintaining entirely constant baths containing 
potassium cyanide, and practical experience and a good faculty 
of observation are required if the results of analysis are to be 
utilized for the correction of the baths. The potassium formate 
can neither be removed from the bath nor can it be quanti- 
tatively determined, and since its action in the bath is not 
accurately known, it can only be stated, from practical experi- 
ence, that under normal conditions only about 60 per cent, of 
the deficiency of free potassium cyanide in a copper bath 
should be replaced by pure potassium cyanide. 

Determination of copper. This may be effected by electroly- 
tic or volumetric analysis. 

For the determination of copper by electrolysis, measure off by 
means of the pipette 10 cubic centimeters of the copper bath, 
and allow the fluid to run into a porcelain dish having a capac- 
ity of 150 to 200 cubic centimeters. Add 10 cubic centimeters 
of pure strong hydrochloric acid, cover the dish with a watch 
glass, and heat upon the water bath. When evolution- of gas 
ceases, carefully remove the watch glass, rinse off adhering 
drops with a small quantity of distilled water into the dish, and 
evaporate the contents of the latter nearly to dryness. Now 
add about 1 cubic centimeter of strong nitric acid, swing the 
dish so that all portions of the residue are moistened by the 
acid, heat for a short time, and then add 32 cubic centimeters 
of pure dilute sulphuric acid (1 part acid, 2 parts water), with 
which the contents of the dish are heated, until every trace of 
odor of hydrochloric and nitric acids has disappeared. Now 
pour the copper solution into the platinum dish serving for 
electrolysis, rinse the porcelain dish with distilled water, add- 
ing the wash-water to the contents of the platinum dish, fill the 
latter up to within 1 centimeter of the rim with water, add 2 cubic 



278 ELECTRO-DEPOSITION OF METALS. 

centimeters of pure concentrated nitric acid and electrolyze 
with a current-strength of ND 100 = 1 ampere, i. e., 1 ampere 
for 100 square centimeters surface of the platinum dish which 
serves as cathode. 

The copper separates with a bright red color, adhering 
firmly to the platinum dish which is connected with the nega- 
tive pole of the source of current. That the separation of cop- 
per is finished is recognized by a narrow strip of platinum 
sheet, when suspended in the platinum dish, showing in 15 
minutes no trace of coppering ; or by a few drops of the solu- 
tion when brought together with a drop of yellow prussiate of 
potash solution producing no red coloration. 

When by one of the above mentioned means the complete 
separation of the copper has been ascertained, the platinum 
dish is washed, without interruption of the current, the water 
removed by rinsing the dish with absolute alcohol, and the lat- 
ter removed by rinsing with ether. Dry for a short time in an 
air bath at 21 2° F., and weigh the dish together with the pre- 
cipitate of copper. By deducting the weight of the dish, the 
weight of the copper is obtained, and, since 10 cubic centime- 
ters of the bath were electrolyzed, the weight of the copper 
multiplied by 100 gives the contents of copper in grammes in 
I liter of copper bath. 

The volumetric determination of copper is based upon the 
principle that solution of sulphate or chloride of copper forms, 
with potassium iodide, copper iodide, whilst free iodine is at 
the same time formed, one atom of liberated iodine correspond- 
ing to one molecule of copper salt. This free iodine is de- 
termined by titration with a solution of sodium hyposulphite of 
known content, and the content of copper is calculated from 
the number of cubic centimeters of the solution used. For the 
recognition of the final reaction, the blue coloration, which 
originates when starch solution combines with free iodine is 
utilized. There are required a decinormal iodine solution 
which contains per liter exactly 12.7 grammes of re-sublimated 
iodine dissolved in potassium iodide, and a decinormal solution 



DEPOSITION OF COPPER, BRASS AND BRONZE. 279 

of sodium hyposulphite of which 10 cubic centimeters diluted 
with water and compounded with a small quantity of starch 
solution must exactly use 10 cubic centimeters of iodine solu- 
tion to give a permanent blue coloration by the formation of 
iodine-starch. 

The mode of operation is as follows : Heat in a porcelain 
dish 10 cubic centimeters of the copper bath with 10 cubic 
centimeters of strong hydrochloric acid, evaporate nearly to 
dryness with 1 cubic centimeter of strong nitric acid and 2 
cubic centimeters of hydrochloric acid, and heat upon the 
water bath until the nitric acid is entirely removed. The resi- 
due is dissolved in water with the addition of a small quantity 
of dilute hydrochloric acid. The clear solution is brought into 
a measuring flask holding ioo cubic centimeters, the dish is 
rinsed with water, the free acid neutralized by the addition of 
dilute soda lye until a precipitate of bluish copper hydrate 
commences to separate, which after vigorous shaking does not 
disappear. Now add, drop by drop, hydrochloric acid until the 
precipitate just dissolves, fill the flask up to the 100 centimeter 
mark with water, and mix by shaking. Of this solution bring 
by means of the pipette 10 cubic centimeters into a glass of 
100 cubic centimeters capacity and provided with a glass 
stopper, add 10 cubic centimeters of a 10 per cent, potassium 
iodide solution, dilute with a small quantity of water, close the 
glass with the stopper, and let it stand for 10 minutes. Now 
add from a burette decinormal solution of sodium hyposulphite 
until the iodine solution has become colorless, and then add a 
few cubic centimeters more. Next bring into the flask a few 
drops of starch solution, and then add from another burette 
decinormal iodine solution until a blue coloration is just ap- 
parent. By deducting the cubic centimeters of iodine solution 
used from the cubic centimeters of sodium hyposulphite solu- 
tion, it will be known how many cubic centimeters of the latter 
solution have been used for fixing the iodine liberated by 
the reciprocal action between copper solution and potassium 
cyanide solution. Since I cubic centimeter of a sodium hypo- 



28o , ELECTRO-DEPOSITION OE METALS. 

sulphite solution, which is equivalent to the decinormal iodine 
solution, corresponds to 0.0063 gramme of copper, therefore, 
as 1 cubic centimeter of the bath has been titrated, the num- 
ber of cubic centimeters found has to be multiplied by 6.3 to 
find the content of copper per liter of copper bath. 

Suppose to 10 cubic centimeters of the copper solution 
mixed with potassium iodide had been added 2.8 cubic centi- 
meters of sodium hyposulphite solution, and for titrating back 
the excess 0.7 cubic centimeter of iodine solution had been 
used up to the appearance of the blue coloration, then 2.8 — 
0.7 = 2.1 centimeters have been used, which multiplied by 6.3 
gives 13.3 grammes as the content of copper per liter of bath. 

If now a deficiency of copper has been established by one or 
the other method, the original content of copper can be readily 
restored by the addition of crystallized potassium copper cy- 
anide. This salt, when pure, contains about 30 per cent, copper. 

Suppose, when first prepared, the bath contained 1 5 grammes 
of copper per liter, and it has been shown by analysis that it 
contains only 13.3 grammes, then a deficiency of 1.7 grammes 
of copper has to be made up. Since 100 grammes of potas- 
sium copper cyanide contain 30 grammes of copper, then 

30: 100= 1.7: X 

x = 3-57> 

and hence 3.57 grammes of potassium copper cyanide per liter 
have to be dissolved in the bath. 

2. Deposition of Brass {Cuivre-poli Deposit). 

Brass is an alloy of copper and zinc, whose color depends on 
the quantitative proportions of both metals. The alloys known 
as yellow brass, red brass {similor, tombac), consist essentially 
of copper and zinc, while those known as bell metal, gun metal 
and the bronzes of the ancients are composed of copper and tin. 
Modern bronzes contain copper, zinc and tin. 

The behavior of brass towards acids is nearly the same as 
that of copper. It oxidizes, however, less readily in the air, is 



DEPOSITION OF COPPER, BRASS AND BRONZE. 28 1 

harder than copper, malleable, and can be rolled and drawn 
into wire. 

Brass baths. — According to the plan pursued in this work 
only the most approved formulae, the greater portion of which 
has been practically tested, will be given. There exist a large 
number of directions for brass baths ; but we share the opinion 
of Roseleur, that a brass bath containing copper and zinc salts 
in nearly equal proportions is the most suitable and least sub- 
ject to disturbances. A brass bath is to be considered as a 
mixture of solutions of copper cyanide and zinc cyanide, or of 
other copper-zinc salts in the most suitable solvent; and since 
a solution of copper cyanide requires a different current- 
strength from one of zinc salt, it will be seen that according to 
the greater or smaller current-strength, now more of the one, 
and now more of the other, metal is deposited, which, of course, 
influences the color of the deposit. Hence the proper regulation 
of the current is the chief condition for obtaining beautiful 
deposits, let the bath be composed as it may. 

For all baths containing more than one metal in solution, it 
may be laid down as a rule that the less positive metal is first 
deposited. In a brass bath copper is the negative, and zinc the 
positive, metal ; and hence a weaker current deposits more 
copper, in consequence of which the deposit becomes redder, 
while, vice versa, a more powerful current decomposes besides 
the copper solution also a larger quantity of zinc solution and 
reduces zinc, the color produced being more pale yellow to 
greenish. By bearing this in mind it is not difficult to obtain 
any desired shades within certain limits. 

I. Brass bath according to Roseleur. — Blue vitriol and zinc 
sulphate (white vitriol), of each 5^ ounces, and crystallized 
carbonate of soda 15^ ounces. Crystallized carbonate of 
soda and crystallized bisulphite of soda, of each 7 ounces, 98 
per cent, potassium cyanide 8^ ounces, arsenious acid 30^ 
grains, water 10 quarts. 

The bath is prepared as follows : In 5 quarts of warm water 
dissolve the blue vitriol and the zinc sulphate ; and in the other 



282 ELECTRO-DEPOSITION OF METALS. 

5 quarts the 15^ ounces of carbonate of soda; then mix both 
solutions, stirring constantly. A precipitate of carbonate of 
copper and carbonate of zinc is formed, which is allowed 
quietly to settle for 10 to] 12 hours, when the supernatant clear 
fluid is carefully poured off, so that nothing of the precipitate 
is lost. Washing the precipitate is not necessary. The clear 
fluid poured off is of no value and is thrown away. Now add 
to the precipitate so much water that the resulting fluid 
amounts to about 6 quarts, and dissolve in it, with constant 
stirring, the carbonate and bisulphite of soda, adding these 
salts, however, not at once, but gradually, in small portions, to 
avoid foaming over by the escaping carbonic acid. Dissolve 
the potassium cyanide in 4 quarts of cold water and add this 
solution, with the exception of about x / 2 pint, in which the 
arsenious acid is dissolved with the assistance of heat, to the 
first solutions, and finally add the solution of arsenious acid in 
the y 2 pint of water retained, when the bath should be clear 
and colorless. If after continued stirring, particles of the pre- 
cipitate remain undissolved, carefully add somewhat more 
potassium cyanide until solution is complete. 

Fresh brass baths work, as a rule, more irregularly than any 
other baths containing cyanide, the deposit being either too red 
or too green or gray, while frequently one side of the object is 
coated quite well, and the other not at all. To force the bath 
to work correctly it must be thoroughly boiled, the water which 
is lost by evaporation being replaced by the addition of dis- 
tilled water or pure rain water. If boiling is to be avoided, the 
bath, as previously mentioned, is worked through for hours, 
and even for days, with the current, until an object suspended 
in it is correctly brassed. 

The addition of a small quantity of arsenious acid is claimed 
to make the brassing brighter; but the above-mentioned pro- 
portion of 30^ grains for a 10 quart bath must not be ex- 
ceeded, as otherwise the color of the deposit would be too light 
and show a gray tone. 

II. Crystallized carbonate of soda 10^ ounces, crystallized 



DEPOSITION OF COPPER, BRASS AND BRONZE. 283 

bisulphite of soda 7 ounces, neutral acetate of copper 4.4 
ounces, crystallized chloride of zinc 4.4 ounces, 98 per cent, 
potassium cyanide 14. 11 ounces, arsenious acid 30^ grains, 
water 10 quarts. 

The preparation of this bath is more simple than that of the 
preceding. 

Dissolve the carbonate and bisulphite of soda in 4 quarts of 
water, then m'x the acetate of copper and chloride of zinc with 

2 quarts of water, and gradually add this mixture to the solu- 
tion of the soda salts. Next dissolve the potassium cyanide in 
4 quarts of water, and add this solution to the first, retaining, 
however, a small portion of it, in which dissolve the arsenious 
acid with the assistance of heat. Finally add the arsenious 
acid solution, when the bath will become clear. Boiling the 
bath, or working it through with the current, is also required. 

For brassing iron in this bath, the quantity of carbonate of 
soda may be increased up to 35 ozs. for a 10-quart bath. This 
is also permissible, when in plating zinc articles with a heavy 
deposit of brass, frequent scratch-brushing is to be avoided. 
It would seem that a large content of carbonate of soda in the 
bath retards to a considerable extent the brass color from 
changing into a discolored brown, though the brilliancy of the 
deposit appears to suffer somewhat. When boiled for 1 to 2 
hours, or worked through with the current for 10 to 12 hours, 
the bath prepared according to formula II. works very well. 
It requires a current of 0.5 to 0.55 ampere, with a tension of 
3.5 to 4 volts per 15^ square inches of surface. 

Cuprous sulphide, mentioned under copper baths, may also 
be advantageously used for the preparation of brass baths, a 
suitable formula being as follows : 

III. Pure crystallized zinc sulphate (zinc vitriol or white 
vitriol) ^y 2 ozs., crystallized carbonate of soda 7^ ozs., neu- 
tral crystallized bisulphite cf soda 9^ ozs., ammonia-soda 1^ 
ozs., 99 per cent potassium cyanide 3 ozs., cuprous sulphide 

3 ozs., water 10 quarts. 

The bath is prepared as follows : Dissolve the zinc sulphide 



284 ELECTRO-DEPOSITION OF METALS. 

in 5 quarts of the water, and the carbonate of soda in 4 quarts 
of warm water, and mix the two solutions. When the precipi- 
tate of zinc carbonate, which is formed, has completely settled, 
siphon off the supernatant fluid as much as possible, add 5 
quarts of water, and then the ammonia-soda. In the other 5 
quarts of water dissolve the potassium cyanide and the neutral 
bisulphide of soda, stir in the cuprous sulphide, and when so- 
lution is complete, add this solution to the first, when by vig- 
orous stirring the carbonate of zinc will also dissolve. 

This bath yields beautiful pale yellow deposits of a warm 
brass tone. 

IV. Crystallized carbonate of soda ioj^ ozs., crystallized 
bisulphite of soda 7 ozs., copper cyanide and zinc cyanide of 
each 3*^ ozs., water 10 quarts, and enough 98 per cent, po- 
tassium cyanide to render the solution clear. 

To prepare the bath dissolve the carbonate and bisulphite of 
soda in 2 to 3 quarts of water, rub in a porcelain mortar the 
copper cyanide and zinc cyanide with a quart of water to a 
thin paste, add this paste to the solution of the soda salts, and 
finally add, with vigorous stirring, concentrated potassium 
cyanide solution until the metallic cyanides are dissolved. 
Dilute the volume to 10 quarts, and, for the rest, proceed as 
given for formulas I. and II. 

For brassing zinc exclusively, Roseleur recommends the fol- 
lowing bath: 

V. Dissolve 9^ ozs. of crystallized bisulphite of soda and 
14 ozs. of 70 per cent, potassium cyanide in 8 quarts of water, 
and add to this solution one of 4^ ozs. each of neutral acetate 
of copper and crystallized chloride of zinc, 5^ ozs. of aqua 
ammonia, and 2 quarts of water. 

For brassing cast-iron, wrought-iron, and steel, Gore highly 
recommends the following composition: — 

VI. Dissolve 35 J^ ozs. of crystallized carbonate of soda, 7 
ozs. of crystallized bisulphite of soda, 13 ]/^ ozs. of 98 per cent, 
potassium cyanide in 8 quarts of water; then add, with con- 
stant stirring, a solution of fused chloride of tin 3J^ ozs., and 



DEPOSITION OF COPPER, BRASS AND BRONZE. 285 

neutral acetate of copper 4^ ozs., in 2 quarts of water. Boil 
and filter. This bath works best with a current of 3.75 volts. 
According to Norris and Johnson, a good brass bath is said 
to be obtained as follows: — 

VII. Carbonate of ammonia 3S/i ozs -> 7° P er cent, potas- 
sium cyanide $$% ozs., copper cyanide and zinc cyanide each 
2J^ ozs., water 10 quarts. 

The large content of potassium cyanide in this bath is unin- 
telligible. 

A solution for transferring any copper-zinc alloy which serves 
as anode is composed, according to Hess, as follows \—r- 

VIII. Bisulphite of soda 14^ ozs., crystallized sal ammoniac 
9^4 ozs., 98 per cent, potassium cyanide 2^ ozs., water 10 
quarts. 

Cast metal plates are to be used as anodes. The transfer 
begins after a medium strong current, has for a few hours, 
passed through the bath. This bath is also well adapted for 
the deposition of tombac, with the use of tombac anodes. 
Most suitable current-tension, 3 to 3.5 volts. 

IX. For brassing all kinds of metals and large as well as 
small objects, Pfanhauser recommends the following bath : 
Water 10 quarts, calcined carbonate of soda 5 ozs., calcined 
sulphate of soda 7 ozs.j^cid. sodium sulphite 7 ozs., potassium 
copper cyanide 7 ozs., potassium zinc cyanide 7 ozs., 100 per 
cent, potassium cyanide 0.35 oz., ammonium chloride 0.7 oz. 

The bath is prepared as follows: Pour one-half of the quan- 
tity of water (cold) into the tank intended for the reception of 
the brass bath. Dissolve, stirring vigorously, the carbonate 
and sulphate of soda in five times their quantity of warm water 
(122 F.), and pour the solution into the tank. Dissolve the 
acid sodium sulphite in five times its quantity of warm water 
(122 F.), stirring constantly, pour the solution slowly into 
the tank and stir until effervescence caused by mixing the two 
solutions ceases. The potassium copper cyanide, potassium 
zinc cyanide and potassium cyanide are together dissolved in 
five times their quantity of warm water (122 F.) and added 



286 ELECTRO- DEPOSITION OF METALS. 

to the solution in the tank, stirring constantly. Finally dis- 
solve the ammonium chloride in \2}i times its quantity of 
water, pour the solution into the vat, and mix thoroughly by 
stirring. When all the salts are dissolved, the bath is ready 
for use. 

The temperature of the bath should be between 68° and JJ° 
F. For brassing zinc the current should have a strength of 2*4 
volts, for iron 3 volts, for chains 3 to 3 ^ volts, and for small 
articles en masse 4 volts. Density of the current, 0.5 ampere. 

Brassing in this bath succeeds equally well with all kinds of 
metals, the result being a uniform deposit of metal while the 
color, even of thick deposits, is a fiery sad yellow. Small 
articles, which are suspended en masse in dipping baskets, as 
well as steel chains, and even cast-iron, which is notoriously 
difficult to brass, become rapidly coated in this bath. In case 
the brass anodes become coated with too great an abundance 
of green slime, which decreases during the night when the bath 
is not working, some potassium cyanide, about 1 y 2 drachms 
per quart, should be added. The bath must, of course, be from 
tfme to time supplied with additions of fresh potassium copper 
cyanide and potassium zinc cyanide. 

Brass baths containing potassium cyanide cannot be kept in 
pitched wooden tanks, as the pitch is dissolved by the salt. 

Execution of brassing. — The most suitable current-density 
for this purpose is 0.6 to 0.7 ampere, at 3 to 4 volts. 

As previously mentioned, the color of the deposits depends 
on the proportional quantity in which copper and zinc are 
present, a strong current depositing more zinc and a weak cur- 
rent more copper. By diminishing or increasing the current- 
strength by means of the resistance board, a deposit of a redder 
or more pale yellow to greenish color can be produced. How- 
ever, with a bath which does not contain copper and zinc in 
the correct proportional quantities, and especially with old 
baths long in use, a determined color of the deposit cannot be 
produced with the assistance of the resistance board. In such 
case the content of the metal lacking in the bath, which is re- 



DEPOSITION OF COPPER, BRASS AND BRONZE. 287 

quired for the production of a determined color, must be aug- 
mented by the addition of solution of the respective metallic 
salt in potassium cyanide. 

Suppose a bath which originally contained copper and zinc 
salts in equal proportions has been long in daily use. Now, 
since brass contains more copper than zinc, it is evident that 
more of the former will be withdrawn from the bath than of the 
latter, and finally a limit will be reached when the bath with a 
current suitable for the decomposition of the solution will 
deposit a greenish or gray brass, and with a weaker current 
produce no deposit whatever. The only help in such a case is 
the addition of sufficient solution of copper cyanide in potas- 
sium cyanide, so that, even with quite a powerful current, a 
deposit of a beautiful brass color is produced, the shades of 
which can then again be controlled with the help of the resist- 
ance board. However, it must not be forgotten that every 
addition of a metallic salt momentarily irritates the brass bath, 
making it, so to say, sick, and to confine this phenomenon to 
the narrowest limit, an addition of carbonate and bisulphite of 
soda should at the same time be made, and the bath be worked 
through with the current as previously described, until a test 
shows that it works in a regular manner. 

Annealed sheets of brass not rolled too hard, and of as nearly 
as possible the same composition and color the deposit is to 
show, are used as anodes. The anode-surface should be at 
least twice as large as that of the objects to be brassed, though 
it is best to use as many anodes as the anode-rods will hold. 

As in the copper bath, an abundant formation of slime on 
the anodes indicates the want of potassium cyanide in the bath. 
In this case the evolution of gas bubbles on the objects is very 
slight, and the deposit forms slowly. This is remedied by an 
addition of potassium cyanide. The slow formation of the 
deposit, however, may also be due to a want of metallic salts. 
In this case not only potassium cyanide, but also solution of 
copper cyanide and zinc cyanide in potassium cyanide, has to 
be added. For this purpose prepare a concentrated solution 



288 ELECTRO-DEPOSITION OF METALS. 

of potassium cyanide in water, and a solution of equal parts of 
blue vitriol and zinc sulphate in water. From the latter pre- 
cipitate the copper and zinc as carbonates with a solution of 
carbonate of soda, as given in formula I., p. 281. After allow- 
ing the precipitate to settle, pour off the clear supernatant fluid, 
and add to the precipitate, with vigorous stirring, of the potas- 
sium cyanide solution, until it is dissolved; if heating takes 
place thereby, add from time to time a little cold water. Add 
this solution with a small excess of potassium cyanide, and the 
addition of carbonate or bisulphite of soda, to the bath, and 
boil the latter or work it through with the current. A more 
simple method is to procure copper cyanide and zinc cyanide, 
or concentrated solutions of these combinations, from a dealer 
in such articles. In the first case rub in a mortar equal parts 
of zinc cyanjde and copper cyanide with water to a thickly fluid 
paste. Pour this paste into potassium cyanide solution, con- 
taining about 7 ozs. of potassium cyanide to the quart, as long 
as. the metallic cyanides dissolve quite rapidly by stirring. 
When solution takes place but slowly, stop the addition of 
paste. 

When a brass bath contains too large an excess of potassium 
cyanide* a very vigorous evolution of gas takes place on the 
objects, but the deposit is formed slowly or not at all; besides, 
the deposit formed has a tendency to peel off in scratch- brush- 
ing. In this case the injurious excess has to be removed, which 
is effected by pouring, whilst stirring vigorously, a quantity of 
the above-mentioned thinly fluid paste of zinc cyanide and of 
copper cyanide into the bath. 

To avoid unnecessary repetition we refer, as regards the pro- 
duction of thick deposits, scratch-brushing and polishing of the 
plated articles, to what has been said under " Execution of 
Coppering," the directions given there being also valid for 
brassing. 

The deposition of several metals from a common solution is 
not an easy task, and requires attention and experience. If, 
however, the directions given in this chapter are followed, the 



DEPOSITION OF COPPER, BRASS AND BRONZE. 289 

operator will be able to conduct, after short experience, the 
brassing process with the same success as one in which but one 
metal is deposited. 

In brassing, the distance of the objects to be plated from the 
anodes is of considerable importance. If objects with deep de- 
pressions or high reliefs are suspended in the brass bath, it will 
be found that, with the customary distance of 3 ^ to 5 ^ inches 
from the anodes, the brassing of the portions in relief nearest 
to the anodes will turn out a lighter color than that of the de- 
pressed portions, which will show a redder deposit, the reason 
for this being that the current acts more strongly upon the 
portions in relief, and consequently deposits more zinc than the 
weaker current, which strikes the depressions. To equalize 
the difference, the objects have to be correspondingly further 
removed from the anodes, with lamp-feet up to 9% inches, and 
even more, when a deposit of the same color will be every- 
where formed. 

The brassing of unground iron-castings is especially trouble- 
some, and in order to obtain a beautiful and clean deposit the 
preliminary scratch-brushing has to be executed with special 
care ; but even then the color of the brass deposit will some- 
times be found to possess a disagreeable gray tone. This is 
very likely largely due to the quality of the iron itself, and it is 
advisable first to give the casting a thin coat of nickel or tin, 
upon which a deposit of brass of the usual brilliancy can be 
produced. In baths serving for brassing iron articles, a large 
excess of potassium cyanide must be avoided. It is, however, 
an advantage to increase the content of carbonate of soda. 

Brassing by contact and dipping. — Some authors have given 
directions for brassing by contact — for instance, Bacco, Weil, 
and others — but the results obtained are so unsatisfactory, and 
the process so uncertain, that it is not necessary to enter into 
further details. 

The inlaying with black of brassed articles is done in the 
same manner as described under " Coppering." 

For oxidizing, platinizing, and coloring of brass, see the 
proper chapter. 
19 



290 ELECTRO-DEPOSITION OF METALS. 

Examination of brass baths. The characteristic indications 
by which a deficiency and too large an excess of potassium 
cyanide in the bath, as well as an insufficient content of metal, 
may be recognized, have already been discussed, and it is here 
only necessary to refer to the quantitative determination of the 
separate constituents. 

Free potassium cyanide and the content of copper are deter- 
mined in the same manner as described under copper baths 
containing potassium cyanide. Hence only the determination 
of zinc has here to be considered. For making this determin- 
ation, it is necessary to destroy the cyanide combinations, and 
entirely to remove the copper. For this purpose bring by 
means of the pipette 10 cubic centemeters of the brass bath 
into a porcelain dish, and proceed in the same manner as 
given on p. 277 for the determination of copper by electroly- 
sis. Dissolve the evaporated residue in the dish in water, add- 
ing a few drops of pure hydrochloric acid. Then bring the 
solution into a capacious beaker, dilute with water to about 
250 cubic centimeters, and heat to boiling. Now add about 
10 cubic centimeters of pure dilute sulphuric acid (1 : 10) and, 
stirring constantly, mix with a solution of 2.5 grammes of 
crystallized sodium. Copper sulphide is separated under the 
escape of sulphurous acid. Cover the beaker with a watch 
glass, let it stand for 15 minutes, and then filter off the precip- 
itate. Wash the filter thoroughly with sulphuretted hydrogen 
water, and evaporate the filtrate together with the wash waters 
to about 100 to 150 cubic centimeters. The solution contains 
all the zinc, and can be at once titrated (see below). 

For the determination of zinc by electrolysis, heat the solu- 
tion to boiling, mix it with solution of sodium carbonate in 
excess, and, after the precipitate of basic zinc carbonate has 
settled, filter it off. Dissolve the precipitate in the filter with 
pure dilute sulphuric acid, bring the filtrate together with the 
waters used for thoroughly washing the filter into a clean 
beaker, and neutralize accurately with sodium carbonate. 

Now bring into the platinum dish, previously coppered, 5 



DEPOSITION OF COPPER, BRASS AND BRONZE. 29 1 

grammes of potassium oxalate and 2 grammes of potassium 
sulphate dissolved in a small quantity of water, fill the platinum 
dish up to within 1 centimeter from the rim with distilled water, 
and electrolyze with a current-density of NDiOO = 0.5 ampere. 
The dull, bluish-white deposit of zinc is treated with water, then 
with alcohol and ether, dried in the exsiccator over sulphuric 
acid, and weighed. The determined weight of the zinc deposit 
multiplied by 100 gives the content of zinc in grammes per liter 
of brass bath. 

For the volumetric determination of the zinc > about 100 to 150 
cubic centimeters of the zinc solution resulting after the pre- 
cipitation of the copper are used. The determination is based 
upon the principle that potassium ferrocyanide solution pre- 
cipitates the zinc from the solution, and that complete precipi- 
tation is indicated by an excess of potassium ferrocyanide, 
yielding a brown coloration with uranium acetate. If now the 
content of the potassium ferrocyanide solution is known, the 
quantity of it used gives the content of zinc. It is best to use 
a solution which contains per liter 32.45 grammes of pure crys- 
tallized potassium ferrocyanide, every cubic centimeter of this 
solution corresponding to 0.01 gramme of zinc. Add, stirring 
constantly, from a burette potassium ferrocyanide solution to 
the zinc solution in a beaker until a drop of the fluid brought 
upon a strip of filtering paper previously saturated with uranium 
acetate solution and again dried just shows the commencement 
of a brown coloration. 

Since 10 cubic centimeters of brass bath were used, the 
number of cubic centimeters of potassium ferrocyanide solu- 
tion used gives the quantity of zinc in grammes per liter of 
brass bath. Suppose 16 cubic centimeters of solution have 
been used, this would correspond to 0.16 gramme zinc (0.01x16). 
Hence since 10 cubic centimeters of bath contain 0.16 gramme, 
the bath contains 16 grammes (0.16x100) of zinc per liter. 

If now a deficiency of zinc in the bath has been determined, 
the initial content can be readily restored by an addition of 
pure potassium zinc cyanide, which contains 21 per cent, of 



292 ELECTRO-DEPOSITION OF METALS. 

zinc. The quantity required is determined in the same manner 
as given under copper baths. 

3. Deposition of Bronze. 

The electro-plating of metallic objects with bronze, i. e. y a 
copper-tin alloy, or an alloy of copper, tin, and zinc, is but 
seldom practiced, the bronze tone being in most cases imitated 
by a deposit of brass, with a somewhat larger content of 
copper. 

For coating wrought- and cast-iron with bronze, Gountier 
recommends the following solution: — 

Yellow prussiate of potash ioj^ ozs., cuprous chloride 5^ 
ozs., stannous chloride (tin salt) 14 ozs., sodium hyposulphite 
14 ozs., water 10 quarts. 

According to Ruolz, a bronze bath is prepared as follows : 
Dissolve at 122 to 140 F., cyanide of copper 2.1 1 ozs., and 
oxide of tin 0.7 oz. in 10 quarts of potassium cyanide solution 
of 4 Be. The solution is to be filtered. 

Eisner prepares a bronze bath by dissolving 21 ozs. of blue 
vitriol in 10 quarts of water, and adding a solution of 2^ ozs. 
of chloride of tin in potash lye. 

Salzede recommends the following bath, which is to be used 
at between 86° and 95 ° F. : Potassium cyanide $j4 ozs., car- 
bonate of potash 3$% ozs., stannous chloride (tin salt) 0.42 
oz., cuprous chloride ]/ 2 oz., water 10 quarts. 

Weil and Newton claim to obtain beautiful bronze deposits 
from solutions of the double tartrate of copper and potash, and 
the double tartrate of the protoxide of tin and potash, with 
caustic potash, but fail to state the proportions. 

The above formulae are here given with all reserve, since ex- 
periments with them failed to give satisfactory results. With 
Gountier's, Ruolz's, and Eisner's baths no deposit was ob- 
tained, but only a strong evolution of hydrogen, while even 
with a strong current Salzede's bath did not yield a bronze 
deposit, but simply one of tin. 

The following method of preparing a bronze bath may be 



DEPOSITION OF COPPER, BRASS AND BRONZE. 293 

recommended : Prepare, each by itself, solutions of phosphate 
of copper and stannous chloride (tin salt) in sodium pyrophos- 
phate. From a blue vitriol solution precipitate, with sodium 
phosphate, phosphate of copper, allow the latter to settle, and 
after pouring off the clear supernatant fluid bring it to solution 
by concentrated solution of sodium pyrophosphate. On the 
other hand, add to a saturated solution of sodium pyrophos- 
phate solution of tin salt as long as the milky precipitate formed 
dissolves. Of these two metallic solutions, add to a solution of 
sodium pyrophosphate, which contains about 1 ^ ozs. of the 
salt to the quart, until the precipitate appears quickly and of 
the desired color. For anodes, use cast bronze plates, which 
dissolve well in the bath. Some sodium phosphate has from 
time to time to be added to the bath, and if the color becomes 
too light, solution of copper, and if too dark, solution of tin. 

¥ ox deposits of tombac Hess's bath (formula VII., Deposition 
of Brass) with anodes of plate or sheet tombac can be recom- 
mended ; 3 to 3.5 volts being the most suitable tension of the 
current for the decomposition of the bath. 

For nickel bronze, see p. 247. 

The execution of bronzing requires the same attention and 
manipulations as given for Deposition of Brass. 



CHAPTER IX. 

DEPOSITION OF SILVER. 

Properties of silver. — Pure silver is the whitest of all known 
metals. It takes a fine polish, is softer and less tenacious than 
copper, but harder and more tenacious than gold. It is very 
malleable and ductile, and can be obtained in exceedingly thin 
leaves and fine wire. Its specific gravity is 10.48 to 10.5, 
according to whether it is cast or hammered. It melts at 
about 1832 F. It is unacted upon by the air, but in the 
atmosphere of towns it gradually becomes coated with a film 
of silver sulphide. It is rapidly dissolved by nitric acid, 
nitrogen dioxide being evolved. Hydrochloric acid has but 
little action upon it even at boiling heat ; when heated with 
concentrated sulphuric acid it yields sulphur dioxide and silver 
sulphate. 

Chlorine acts upon silver at the ordinary temperature. 
Silver has great affinity for sulphur, and readily fuses with it 
to silver sulphide. Sulphuretted hydrogen blackens silver, 
brown-black silver sulphide being formed (tarnishing of silver 
in rooms in which gas is burned). Such tarnishing is most 
readily removed by potassium cyanide solution. 

Watery chromic acid converts silver into red silver chromate, 
and this conversion is made use of for the recognition of silver- 
ing. By touching silver or genuine silver-plating with a drop 
of a solution obtained by dissolving potassium bichromate in 
nitric acid of 1.2 specific gravity, a red stain is formed. 

Electro-plating with silver was, of all electro-metallurgical 
processes, the first which was carried on on a large scale, and 
the figures given below are an indication of the dimensions it 
has reached. Bouilhet stated before the Electrical Congress, 

(294) 



DEPOSITION OF SILVER. 295 

that in the establishment of Christofle & Co., of Paris, more 
than 13,200 lbs. of silver are annually consumed for plating 
purposes. Since 1842, when their business was established, 
up to 1885, 371,800 lbs. of silver had been used in electro- 
plating. It may be supposed that other large celebrated 
establishments use at least the same amount, and it may 
safely be said that the quantity of silver consumed annually in 
Europe and America for plating purposes amounts to from 
330,000 to 352,000 lbs. 

Silver baths. — The longer an electro-plating process has 
been carried on, the greater, as a rule, the number of existing 
formulae for baths will be; but silver baths are an exception to 
this rule. If it is taken into consideration that silver-plating 
has been practically carried on for about sixty years, the num- 
ber of formulae might be expected to be at least equal to those 
for nickel-plating, which is of much more recent origin. Such, 
however, is not the case, and chiefly for the reason that the 
attempts to improve the silver baths, which were made either 
with a view to banish the poisonous potassium cyanide from 
the silver-plating industry, or otherwise to advance the plating 
process, could absolutely show no better results than the baths 
used by the first silver-platers. However, that attempts to 
make such improvements have not been entirely abandoned, is 
shown by Zinin's proposition to substitute solution of silver 
iodide in potassium iodide for a solution containing potassium 
cyanide. Experiments, however, have shown that the results 
with this process, like with many other modern methods, are 
not equal to those obtained with the approved baths which 
have stood the test of time. Hence, only formulae for the 
most approved baths will here be given. 

Silver bath for a heavy deposit of silver (plating by weight). 
— I. 98 per cent, potassium cyanide 14 ozs., fine silver as silver 
chloride S^( ozs., distilled water 10 quarts. 

la. 98 per cent, potassium cyanide 8^ ozs., fine silver as 
silver cyanide 8J^ ozs., distilled water 10 quarts. 

Before describing the preparation of the bath a few words may 



296 ELECTRO-DEPOSITION OF METALS. 

be said in regard to the old dispute whether it is preferable to 
use silver cyanide or silver chloride. Without touching upon 
all the arguments advanced, it may be asserted, by reason of 
conscientious comparative experiments, that the results are the 
same, and that the life of the bath is also the same, whether one 
or the other salt has been used in its original preparation. 
From a theoretical standpoint, silver cyanide must be given the 
preference ; but as the disadvantages in respect to the life of 
the bath ascribed by some to silver chloride do not exist, it 
might be advisable for those who prepare their own baths to 
use silver chloride. 

Preparation of bath I. with silver chloride. — Dissolve 14 ozs. 
of chemically pure nitrate of silver, best the crystallized, and not 
the fused, article, in 5 quarts of water, and add to the solution 
pure hydrochloric acid, or common salt solution, with vigorous 
stirring or shaking, until a sample of the fluid filtered through 
a paper filter forms no longer a white caseous precipitate of 
silver chloride when compounded with a drop of hydrochloric 
acid. These, as well as the succeeding operations, until the 
silver chloride is ready, have to be performed in a darkened 
room, as silver chloride is partially decomposed by light. Now 
separate the precipitate of silver chloride from the solution by 
filtering, using best a large bag of close felt, and wash the pre- 
cipitate in the felt bag with fresh water. Continue the washing 
until blue litmus-paper is no longer reddened by the wash- 
water, if hydrochloric acid was used for precipitating, or, if 
common salt solution was used, until a small quantity of the 
wash-water, on being mixed with a drop of lunar caustic solu- 
tion, produces only a slight milky turbidi;y and no precipitate. 
Now bring the washed silver chloride in portions from the felt 
bag into a porcelain mortar, rub it with water to a thin paste, 
and pour the latter into the potassium cyanide solution consist- 
ing of 14 ozs. of 98 per cent, potassium cyanide in 5 quarts of 
water, in which, by vigorous stirring, the silver chloride gradu- 
ally dissolves. All the precipitated silver chloride having been 
brought into solution, dilute with water to 10 quarts of fluid, 



DEPOSITION OF SILVER. 297 

and boil the bath, if possible, for an hour, replacing the water 
lost by evaporation. A small quantity of black sediment con- 
taining silver thereby separates, from which the colorless fluid 
is filtered off. The sediment is added to the silver residues, 
and is worked together with them for the recovery of the silver 
by one of the methods to be described later on. 

Preparation of bath la. with silver cyanide. — Dissolve 14 
ounces of chemically pure crystallized nitrate of silver in 5 
quarts of water, and precipitate the silver with prussic acid, 
adding the latter until no more precipitate is produced by the 
addition of a few drops of prussic acid to a filtered sample of 
the fluid. Now filter, wash, and proceed for the rest exactly 
as stated for the bath with silver chloride, except that only 8J^ 
ounces of potassium cyanide are taken for dissolving the silver 
cyanide. In 'working with prussic acid avoid inhaling the 
vapor which escapes from the liquid prussic acid, especially in 
the warm season of the year; and be careful the acid does not 
come in contact with cuts on the hands. It is one of the most 
rapidly-acting poisons. 

Silver cyanide may also be prepared as follows: Dissolve 
14 ounces of chemically pure crystallized nitrate of silver in 5 
quarts of water, and add moderately concentrated potassium 
cyanide solution until no more precipitate is formed, avoiding, 
however, an excess of the precipitating agent, as it would again 
dissolve a portion of the silver cyanide. The precipitated 
silver cyanide is filtered off, washed and dissolved in potassium 
cyanide, as above described. 

The preparation of the silver bath according to the above 
formulae is more conveniently effected by using pure crystal- 
lized potassium silver cyanide in the following proportions : 

lb. 98 per cent, potassium cyanide, 6% to 7 ozs. ; crystal- 
lized potassium silver cyanide, 17^ ozs.; distilled water, 10 
quarts. The salts are simply dissolved in the cold water. 

The baths prepared according to formulae I, la or lb serve 
chiefly for the production of a heavy deposit upon German 
silver articles, especially table and other household utensils. 



298 ELECTRO-DEPOSITION OF METALS. 

Of course, they may also be used for plating other metals by 
weight. 

Silver bath for ordinary electro-silvering. — II. 98 per cent, 
potassium cyanide, 6% to 7 ounces; fine silver (as silver 
nitrate or chloride), 35^ ounces; distilled water, 10 quarts. 

To prepare the bath dissolve 5*4 ounces of chemically pure 
crystallized nitrate of silver in 5 quarts of distilled water; in the 
other 5 quarts of water dissolve the potassium cyanide, and 
mix both solutions. Or, if chloride of silver is to be used, pre- 
cipitate the solution of 3^ ounces of the silver salt in the same 
manner as given for formula I. ; wash the precipitated chloride 
of silver, and dissolve it in the potassium cyanide solution. 

Ha. 98 per cent, potassium cyanide i| ozs., crystallized 
potassium silver cyanide 7 ozs., distilled water 10 quarts. 

Dissolve the salts in the cold water. 

Tanks of stone-ware or enameled iron are only to be used 
for silver baths. 

Treatment of the silver baths. — Silver anodes. Frequently 
the error is committed of adding too much potassium cyanide 
to the bath. A certain excess of it must be present, and, in 
the formulae given, this has been taken into consideration. 
For dissolving the silver cyanide prepared from 14 ounces of 
nitrate of silver, as given in formula la, only about 5^ ounces 
of potassium cyanide are required, and the consequence of 
working with such a bath devoid of all excess would be that, 
on the one hand, the bath would offer considerable resistance 
to the current, and, on the other, that the deposit would not be 
uniform and homogeneous. Hence with the use of a medium 
strong current about 30 to 35 per cent, more potassium cyanide 
than fine silver is taken. In working with a stronger current 
this excess would, however, be too large, and the deposit would 
not adhere properly and would peel off in scratch-brushing. 
And again, with a weak current the baths can, without disad- 
vantage, stand a larger excess. As a rule, however, the pro- 
portion between fine silver and potassium cyanide in the above 
formulae may be considered as normal, and the current-strength 



DEPOSITION OF SILVER. 299 

will have to be regulated so that a deposit of fine structure, 
which adheres firmly, is formed. The most suitable current- 
strength per i$*4 square inches of surface is 0.25 to 0.15 
ampere, and 0.5 to 0.75 volt tension; the tension of a Daniell 
element being more than sufficient for the decomposition of the 
silver bath. On account of the silver bath requiring a current 
of slight electro-motive force the Smee element, which yields 
0.48 volt, is much liked for silver-plating in this country and in 
England. The Bunsen element may, however, also be used if 
the surface to be plated is made to correspond with the energy 
of such an element; or if a resistance board is placed in the 
circuit, which is advisable in all cases. On account of the slight 
electro-motive force required in silver-plating larger surfaces 
of objects, the elements are not to be coupled one after the 
other for electro-motive force, but alongside one another for 
quantity. In no case must an evolution of hydrogen be per- 
ceptible on the articles, and the current must be more weak- 
ened the larger the excess of potassium cyanide in the bath. 

Whether too much, or not enough, potassium cyanide is 
present in the bath is indicated by the appearance of the plated 
objects and the properties of the deposit, as well as by the 
behavior of the anodes in the bath during and after silvering. 

It may be accepted, as a rule, that with a moderate current 
the object must, in the course of 10 to 15 minutes, be coated 
with a thin, dead white film of silver. If this be not the case, 
and the film of silver shows a meager bluish-white tone, potas- 
sium cyanide is wanting. However, if, on the other hand, the 
dead white deposit forms within 2 or 3 minutes, and shows a 
crystalline structure, or a dark tone playing into gray-black, 
the content of potassium cyanide in the bath is too large, pro- 
vided the current is not excessively strong. If copper and 
brass become coated with silver without the co-operation of 
the current, the bath contains also too much potassium 
cyanide. 

In silver-plating, even if the objects are to be thinly coated, 
insoluble platinum anodes should never be used, but only 



300 ELECTRO-DEPOSITION OF METALS. 

anodes of fine silver, which are capable of maintaining the con- 
tent of silver in the bath quite constant. From the behavior 
and appearance of the anodes, a conclusion may also be drawn 
as to whether the content of potassium cyanide in the bath is 
too large or too small. If the anodes remain silver-white dur- 
ing plating, it is a sure sign that the bath contains more potas- 
sium cyanide than is necessary and desirable ; but, if they turn 
gray or blackish, and retain this color after plating, when no 
current is introduced into the bath for a quarter of an hour or 
more, potassium cyanide is wanting. On the other hand, the 
correct content of potassium cyanide is present when the 
anodes acquire during the plating process a gray tone, which, 
after the interruption of the current, gradually changes back to 
a pure white. 

The proposition to use steel plates in place of silver anodes 
cannot be approved, and as regards such anodes the reader is 
referred to what is said under " Deposition of Gold." 

If it is shown by the process of silvering itself, or by the ap- 
pearance of the articles or of the anodes, that potassium cyanide 
is wanting in the bath, it should be immediately added, though 
never more than 30 to 37 }4 grains per quart of bath at one 
time, so as to avoid going to the other extreme. Too large a 
content of potassium cyanide is remedied by adding to the 
bath, stirring constantly, a small quantity of cyanide or chloride 
of silver rubbed with water to a thinly-fluid paste, whereby the 
excess is rendered harmless in consequence of the formation of 
the double salt of silver and potassium cyanide. Instead of 
such addition, the current may, however, be used for correcting 
the excess. For this purpose suspend as many silver anodes 
as possible to the anode-rods, but only a single anode as an 
object to the object-rod, and allow the current to pass for a 
few hours through the bath, whereby the excess of potassium 
cyanide is removed and rendered harmless by the dissolving 
silver. 

The bath can be kept quite constant by silver anodes, pro- 
vided potassium cyanide be regularly added at certain inter- 



DEPOSITION OF SILVER. 301 

vals, and the anode-surface is equal to that of the objects to be 
plated. But since, on account of the expense, a relatively 
small anode-surface is frequently used, the content of silver in 
a bath continuously worked will finally become lower, and 
augmentation, by the addition of silver, will be required. The 
manner of effecting this augmentation depends on whether the 
baths are used for plating by weight or for lighter silvering, or 
whether the baths are worked, without stopping, from morning 
till evening. For replacing the deficiency in baths prepared 
according to formulae I and la, it is advisable to use exclusively 
solution of silver cyanide in potassium cyanide, or of crystal- 
lized potassium silver cyanide in water. 

It has previously been mentioned that with proper treatment 
baths made with chloride of silver have the same duration of 
life as those prepared with silver cyanide. The chief feature 
of such proper treatment is not to use chloride of silver dis- 
solved in potassium cyanide for augmenting the content of 
silver, but to employ silver cyanide instead, since by the use of 
the former the bath thickens in consequence of the potassium 
chloride which is simultaneously introduced, and would offer 
greater resistance to the current. The fear expressed by some 
authors that a crystalline separation of potassium chloride, and 
the consequent formation of a deposit full of holes might take 
place, is, however, not well founded, since potassium chloride 
is one of the most soluble salts, and shows but little tendency 
to separate in crystals from aqueous solutions. The gradual 
thickening above referred to is, however, a disadvantage, which 
shows itself by the deposit being less homogeneous, and for 
this reason it is advisable, when plating by weight, to use 
silver cyanide in place of the chloride for strengthening the 
silver bath. 

A gradual thickening of the bath may also take place if po- 
tassium cyanide containing potash is used instead of the prep- 
aration free from potash, and of 98 to 99 per cent, purity. Even 
pure fused potassium cyanide produces a thickening of the 
bath, which, however, progresses very slowly. This thickening 



302 ELECTRO-DEPOSITION OF METALS. 

is due to a portion of the excess of potassium cyanide being 
converted by the action of the air into potassium carbonate. 
The latter thus formed must from time to time be neutralized, 
which is generally done with prussic acid, the potassium car- 
bonate being thereby converted into potassium cyanide. In- 
stead of prussic acid, calcium cyanide, or barium cyanide, may 
be added as long as a precipitate of calcium carbonate or 
barium carbonate is formed, the clear solution being separated 
from the precipitate by filtering. 

For augmenting the content of silver in baths prepared ac- 
cording to formula II., solution of nitrate or of chloride of sil- 
ver in potassium cyanide may unhesitatingly be used, since the 
thickening proceeds more slowly on account of the smaller 
content of salt in the bath, and because a cheaper bath can be 
more readily renewed without the sacrifice of money than one 
for heavy deposits. The recovery of silver from old baths is 
effected by one of the methods given later on. 

Since, as mentioned above, the proportion of excess of 
potassium cyanide to the content of silver undergoes changes 
according to the proportion of the object-surface to the anode- 
surface, the temperature of the bath, etc., it becomes necessary 
to add one or the other in order to maintain the proper pro- 
portions and the effective working of the bath. 

To determine whether the bath contains silver and excess of 
potassium cyanide in proper proportions, the following methods 
may be used: Dissolve I gramme (15.43 grains) of chemically 
pure crystallized nitrate of silver in 20 grammes (07 oz.) of 
water and gradually add this solution, whilst constantly stirring 
with a glass rod, to 100 grammes (3.52 ozs.) of the silver bath 
in a beaker, as long as the precipitate of silver cyanide formed 
dissolves by itself. If, after adding the entire quantity of silver 
solution, the precipitate dissolves rapidly, too large an excess 
of potassium cyanide is present in the bath; and vice versa, if 
the precipitate does not completly dissolve, after stirring, 
potassium cyanide is wanting. 

The quantitative determination of content of potassium cyan- 



DEPOSITION OF SILVER. 



303 



ide and of silver will be described later on under " Examination 
of Silver Baths." 

In silver-plating, constant agitation of the strata of fluid is of 
decided advantage, streaks and blooms being otherwise readily 
formed upon the plated objects. To keep the articles in gen- 
tle motion while in the bath, one method is to connect the 
suspending rods to a frame of iron having four wheels, about 3 
inches in diameter, connected to it, which slowly travel to and 
fro to the extent of 3 or 4 inches upon inclined rails attached 
to the upper edges of the tank, the motion, which is both hori- 
zontal and vertical, being given by means of an eccentric wheel 



Fig. 129. 




driven by steam power. By another arrangement, the frame 
supporting the articles does not rest upon the tank, but is sus- 
pended above the bath, and receives a slow swinging motion 
from a small eccentric or its equivalent. In the Elkington 
establishment at Birmingham the following arrangement is in 
use : All the suspending rods of the bath rest upon a copper 
mounting, which, by each revolution of an eccentric wheel, is 
lifted about y^ inch, and then returned to its position. The 
copper mounting is connected to the main negative wire of the 
dynamo-machine by a copper cable. The same object may 



304 ELECTRO-DEPOSITION OF METALS. 

also be attained by giving the articles a horizontal, instead of a 
vertical motion, as shown in Fig. 129, in which the motion is 
produced by an eccentric wheel on the side. 

With equal, if not better, success the mechanically moved 
stirring apparatus which will be described under " Copper 
Galvano-plasty," may be used. In this apparatus several glass 
rods movable around a pivot keep the bath in constant motion. 
Where such a stirring apparatus cannot be conveniently 
arranged, the motion of the bath may be produced by intro- 
ducing, by means of a pump, air on the bottom of the tank. 

A singular phenomenon in regard to silver baths, which 
has not yet been explained, may here be mentioned. A small 
addition of certain, and especially of organic, substances, which, 
however, must not be made suddenly or in too large quanti- 
ties, produces a fuller and better-adhering deposit of greater 
lustre than can be produced in fresh baths. Elkington ob- 
served that an addition of a few drops of bisulphide of carbon 
to the bath made the silvering more lustrous, while others 
claim to have used with success solutions of iodine in chloro- 
form, of gutta-percha in chloroform, as well as heavy hydro- 
carbons, tar, oils, etc. 

Some preparations which have been recommended for this 
" bright" plating may here be given. Bring 6 ozs. of bisulphide 
of carbon into a stoppered bottle and add 1 gallon of the usual 
plating solution. Shake the mixture thoroughly and then set 
it aside for 24 hours. Add 2 ozs. of the resulting solution to 
every 20 gallons of ordinary plating solution in the vat, and 
stir thoroughly. This proportion must be added every day, 
but where the mixture has been used every day, less than this 
may be used at a time. This proportion is claimed to give a 
bright deposit, but by adding a larger amount a dead surface 
may be obtained, very different from the ordinary dead surface. 

Another method of preparing a solution for bright-plating is 
as follows : Put 1 quart of ordinary silver-plating solution into 
a large stoppered bottle. Now add 1 pint of strong solution 
of cyanide, and shake well ; 4 ozs. of bisulphide of carbon are 



DEPOSITION OF SILVER. 305 

then added, as also 2 or 3 ozs. of liquid ammonia, and the 
bottle again well shaken, this operation being repeated every 
two or three hours. The solution is then set aside for about 
24 hours, when it will be ready for use. About 2 ozs. of the 
clear liquid may be added to every 20 gallons of plating solu- 
tion, and well mixed by stirring. A small quantity of the 
brightening solution may be added to the bath every day, and 
the liquid then gently stirred. In course of time the bisulphide 
solution acquires a black color, to modify which a quantity of 
strong cyanide solution, equal to the brightening liquor which 
has been removed from the bottle, should be added each time. 
In adding the bisulphide solution to the plating bath, an excess 
must be avoided, otherwise the latter will be spoilt. Small 
doses repeated at intervals is the safer procedure, and less 
risky than the application of larger quantities, which may ruin 
the bath. 

A very simple way to prepare the brightening solution is to 
put 2 or 3 ozs. of bisulphide of carbon into a bottle which 
holds rather more than half a gallon. Add to this about 3 
pints of old silver solution and shake the bottle well for a 
minute or so. Then nearly fill the bottle with a strong solu- 
tion of cyanide, shake well as before, and set aside for at least 
24 hours. Add about 2 ozs. (not more) of the brightening 
liquor, without shaking the bottle, to each 20 gallons of solu- 
tion in the plating vat. Even at the risk of a little loss from 
evaporation, it is best to add the brightening liquor to the bath 
the last thing in the evening, when the solution should be well 
stirred so as to thoroughly diffuse the added liquor. The 
night's repose will leave the bath in good working order for 
the following morning. 

A silver bath, as shown by experience, becomes without 
doubt bettter in the degree as it takes up small quantities of 
organic substances from the air and from dust; but numerous 
experiments have failed to confirm Elkington's observation 
that the formation of the deposit or its appearance is essentially 
influenced by the addition of bisulphide of carbon or any of the 
20 



306 ELECTRO-DEPOSITION OF METALS. 

above-mentioned solutions of organic origin either in very small 
or considerable quantities. Many baths have been entirely 
spoiled by an attempt to change them into bright working 
baths by the addition of such ingredients, and hence it is best 
to leave such experiments alone. It may, however, be stated 
that by the addition of a few drops of spirits of sal ammoniac, 
fresh silver baths accommodate themselves more rapidly to 
regular performance. 

After plating, the objects frequently show, instead of a pure 
white, a yellow tone, or they become yellow in the air, which is 
ascribed to the formation of basic silver salts in the deposit. To 
overcome this evil it has been proposed to allow the objects to 
remain in the bath for a few minutes after interrupting the cur- 
rent, whereby the basic salts are dissolved by the potassium 
cyanide of the bath ; or the same object is attained by invert- 
ing the electrodes for a few seconds, after plating, thus trans- 
forming the articles into anodes. The electric current carries 
away the basic salt of silver in preference to the metal. This 
operation should, of course, not be prolonged, otherwise the 
silver will be entirely removed from the objects, and will be 
deposited on the anodes. For the same purpose some electro- 
platers hold in readiness a warm solution of potassium cyanide, 
in which they immerse the plated articles for half a minute. 

It has been proposed to add to the silver baths a solution of 
nickelous cyanide in potassium cyanide in order to obtain a 
deposit of a silver-nickel alloy, which is claimed to be dis- 
tinguished by its greater hardness and the property of not turn- 
ing so readily dark. Numerous experiments with solutions of 
cyanide of silver and nickelous cyanide in potassium cyanide in 
all possible proportions, and under various tensions of current 
and subsequent analysis of the deposits obtained, showed, how- 
ever, only inconsiderable traces of nickel in the silver deposit, 
which had but a very slight influence upon the hardness and 
durability of the silver. 

The London Metallurgical Co. endeavors to attain greater 
hardness and power of resistance of the silver by adding zinc 



DEPOSITION OF SILVER. 307 

cyanide or cadmium cyanide, and has given to this process the 
name of areas silver-plating. According to the patent an addition 
of 20 to 30 per cent, of zinc or cadmium to the silver prevents 
the tarnishing of the plating, and besides the deposit is claimed 
to be lustrous and hard. For areas silver-plating the appropriate 
quantity of zinc or cadmium, or a mixture of both metals, is 
converted into potassium-zinc cyanide or potassium-cadmium 
cyanide, and this solution is mixed with a corresponding quan- 
tity of solution of potassium silver cyanide, with a small excess of 
potassium cyanide. Sheets of a silver-zinc or a silver- cadmium 
alloy are used as anodes. 

Some English electro-platers claim that for many articles, 
especially bicycles, areas silver-plating may be substituted for 
nickeling. 

The following experiments may serve as an illustration re- 
garding the value of this process as a substitute for silver-plating 
instruments and articles of luxury: — 

A bath was prepared which contained per quart 231 *4 troy 
grains of fine silver and yj troy grains cadmium in the form of 
cyanide double salts with a small excess of potassium cyanide. 
The most suitable tension of current for the decomposition of 
a pure potassium-cadmium cyanide solution which contained 
per quart 154 troy grains of cadmium with the same excess of 
potassium cyanide as the above-mentioned mixture, was found 
to be 2 volts. 

In electrolyzing the cadmium-silver bath with 0.75 volt, a 
uniform silver-white deposit similar to that of pure silver was at 
first formed. However, after two hours the deeper places of 
the objects suspended in the bath showed crystalline excres- 
cences which felt sandy and could be rubbed off with the 
fingers. After scratch-brushing the articles and again suspend- 
ing them in the bath, these sandy non-adhering metallic de- 
posits were rapidly reformed. An analysis of the deposit 
separated from the articles showed 96.4 per cent, silver, and 
3.2 per cent, cadmium. This deposit could, without difficulty, 
be polished with the steel like a pure silver deposit, and hence 



308 ELECTRO-DEPOSITION OF METALS. 

its hardness would not seem greater than that of pure silver. 
Its capability of resisting hydrogen sulphide as compared with 
that of pure silver was scarcely -greater. 

In another experiment electrolysis was effected with 1.25 
volts. The deposit showed from the start a coarser structure, 
and the formation of the sandy non-adhering deposit took place 
much more rapidly. But, on the other hand, the hardness of 
the separated coherent metal was greater than that of pure 
silver, and also its power of resisting hydrogen sulphide. An 
analysis of the deposit showed 92.1 per cent, silver and 7.8 per 
cent, cadmium. In both cases the deposit was dull like that of 
pure silver. 

With a greater tension of current the quantity of cadmium in 
the deposit increased, and the hardness of the latter became 
correspondingly greater. However, these deposits could not 
be considered serviceable for the above-mentioned purpose, 
because they could not be made of sufficient thickness as re- 
quired for solid silver-plating of forks and spoons. 

Execution of silver-plating — A. Silver-plating by weight. — 
Current-density 0.25 to 0.35 ampere per square decimeter (15.5 
square inches.) Copper, brass, and all other copper alloys may 
be directly plated after amalgamating (quicking), whilst iron, 
steel, nickel, zinc, tin, lead, and Britannia are first coppered or 
brassed, and then amalgamated. 

The mechanical and chemical preparation of the objects for 
the silver-plating process is the same as described on pages 161 
and 169. To obtain well-adhering deposits great care must 
be exercised in freeing the objects from grease and in pickling. 
As a rule, objects to be silver-plated are ground and polished. 
However, polishing must not be carried too far, since the de- 
posit of silver does not adhere well to highly-polished surfaces ; 
and in case such highly-polished objects are to be silvered it is 
best to deprive them of their smoothness by rubbing with 
pumice powder, emery, etc., or by pickling. 

The treatment of copper and its alloys, German silver and 
brass, which have chiefly to be considered in plating by weight, 
is, therefore, as follows: — 



DEPOSITION OF SILVER. 309 

1. Freeing from grease by hot potash or soda lye (1 part of 
caustic alkali to 8 or 10 parts of water), or by brushing with 
the lime-paste mentioned on page 170. 

2. Pickling in a mixture of I part, by weight, of sulphuric 
acid of 66° Be. and 10 of water. This pickling is only required 
for rough surfaces of castings, ground articles being imme- 
diately after freeing from grease treated according to 3. 

3. Rubbing with a piece of cloth dipped in fine pumice 
powder or emery, after which the powder is to be removed by 
washing. 

4. Pickling in the preliminary pickle, rinsing in hot water, 
and quickly drawing through the bright dipping bath (page 
163), and again thoroughly rinsing in several waters. 

5. Amalgamating (quicking) by immersion in a solution of 
mercury, called the quicking solution. This consists of a solu- 
tion of 0.35 ounce of nitrate of mercury in 1 quart of water, to 
which, while constantly stirring, pure nitric acid in small por- 
tions is added until a clear fluid results. A weak solution of 
potassium mercury cyanide in water is, however, to be pre- 
ferred, because the acid-quicking solution mentioned above 
makes the metals brittle. A quicking solution for silver-plating 
by weight consists of: Potassium mercury cyanide, 14 drachms 
to 1 oz. ; 99 per cent, potassium cyanide, 14 drachms ; water, 1 
quart. Care must be taken to bring the quicked objects into 
the bath as rapidly as possible, otherwise thin objects are liable 
to become brittle. The amalgam formed upon the surface 
penetrates to the interior of thin sheets if this action is not 
prevented by an immediate deposition of silver and the forma- 
tion of silver amalgam. In the quicking solution the objects 
remain only long enough to acquire a uniform white coating, 
when — 

6. They are rinsed in clean water, and gone over with a soft 
brush in case the quicking shows a gray, instead of a white 
tone. 

The articles are now brought into the silver bath, and 
secured to the object rods by slinging wires of pure copper or, 



3IO ELECTRO-DEPOSITION OF METALS. 

still better, of pure silver. The latter have the advantage that 
when by reason of a deposit of considerable thickness having 
been formed upon them, they have become useless for suspend- 
ing the articles, they can be directly converted into silver 
nitrate by dissolving in nitric acid, and used for the prepara- 
tion of fresh baths, or for strengthening old baths. 

When certain objects, for instance, forks and spoons are to 
to be plated, copper wires may be bent in the man- 
ner shown in Fig. 130. To prevent the deposition 
A of silver upon the portions of the wire which do not 
HI serve for the purpose of contact, they are coated 
II with fused ebonite mass or gutta percha, only the 
AB^ H ^°°P m wmcn the fork or spoon is hung and the 
gf^i^r upper end for suspending to the object-rod being 
H j a afc . left free. Silver wires are also better for this 
^g^jfe^r purpose. 

Introduce into the bath at first a somewhat more 
powerful current, so that the first deposit of silver takes place 
quite rapidly, and after 3 minutes regulate the current so that in 
10 to 15 minutes the objects are coated with a thin, dull film of 
silver. At this stage take them from the bath, and after seeing 
that all portions are uniformly coated, scratch-brush them with 
a brass brush, which should, however, not be too fine. In do- 
ing this the deposit must not raise up. If at this stage the 
objects stand thorough scratch brushing, raising of the deposit 
in burnishing later on need not be feared. 

Any places which show no deposit are vigorously scratch- 
brushed with the use of pulverized tartar, then again carefully 
cleansed by brushing with lime-paste to remove any impurities 
due to touching with the hands, pickled by dipping in potas- 
sium cyanide solution, rinsed off again, quicked, and after 
careful rinsing returned to the bath. Special care must be had 
not to contaminate the bath with quicking solution, as this 
would soon spoil it. 

The objects now remain in the bath until the deposit has ac- 
quired a weight corresponding to the desired thickness. Knives, 



DEPOSITION OF SILVER. 3 I I 

forks, and spoons receive a deposit of 2.1 1 to 3.52 ozs. of silver 
per dozen, such deposit being produced with elements in 10 to 
[4 hours, and with a dynamo in 4 to 5 hours. According to 
Dr. William H, Wahl, the amount of silver deposited upon the 
several grades of plated table-ware manufactured by the Wil- 
liam Rogers Manufacturing Co., of Hartford, Conn., is as fol- 
lows : 

Per gross. Extra plate. Double plate. Triple plate. 

Teaspoons 48 dwts. 4 ozs. 6 ozs. 

Desertspouns and forks 72 " 6 " 9 " 

Tablespoons and med. forks. . . 96 " 8 " 12 " 

In order to control the weight of the deposit proceed as 
follows: After having removed one of the pans of a sensitive 
beam balance, substitute for it a brass rod, which keeps the 
other pan in equilibrium. Under this rod place a vessel filled 
with pure water and of sufficient diameter and depth to allow of 
the article suspended to the rod dipping entirely into the water 
without touching the sides of the vessel. Suppose now that 
several dozen spoons of the same size and shape are at the 
same time to be provided with a deposit of a determined weight, 
it suffices to control the weight of the deposit of a single spoon, 
and when this has acquired the necessary deposit all the other 
spoons will also be coated with a deposit of silver of the same 
thickness as the test spoon. After quicking and carefully rinsing- 
the spoons, one of them is suspended to the brass rod of the 
balance so that it dips entirely under water. The equilibrium 
is then re-established by placing lead shot upon the pan of the 
scale, and adding the weight corresponding to the deposit the 
spoon is to receive. Now bring the weighed spoon together 
with the rest into the bath, and proceed with the silvering pro- 
cess in the ordinary manner. After some time the weighed 
spoon is taken from the bath, rinsed in water, and hung to the 
brass rod of the scale. If it does not restore the equilibrium 
of the latter, it is returned to the bath, after some time again 
weighed, and so on until its weight corresponds to that of the 



312 



ELECTRO-DEPOSITION OF METALS. 



lead shot and weight placed in the pan of the scale, when it is 
assumed that the balance of the articles have also received their 
proper quantity and that the operation is complete. 

A more complete weighing apparatus is the plating balance 
first used by Brandely and later on improved by Roseleur. 
The apparatus, which is shown in Fig. 131, is designed for 



Fig 




obtaining deposits of silver " without supervision and with 
constant accuracy, and which spontaneously breaks the current 
when the operation is terminated." It is manufactured in 
various sizes, suitable for small or large operations. 

It consists of: 1. A wooden vat, the upper edge of which 
carries a brass winding- rod having a binding screw at one end 



DEPOSITION OF SILVER. 



313 



Fig. 132. 



to receive the positive conducting wire of the battery. From 
this rod the anodes are suspended, which are entirely immersed 
in the solution, and communicate with brass cross-rods by 
means of platinum wire hooks. These cross-rods are flattened 
at their ends so that they may not roll, and at the same time 
have a better contact with the " winding- rod." 2. A cast-iron 
column screwed at its base to the side of the vat, and which 
carries near the top two projecting arms of cast-iron, the ex- 
tremities of which are vertical and forked, and 
may be opened or closed by iron clamps. 
These forks are intended for sustaining the 
beam and preventing the knives from leaving 
their bearings under the influence of too vio- 
lent oscillations. In the middle of the two 
arms are two wedge-shaped recesses of polished 
steel to receive the knife edges of the beam. 
One of the arms of the column carries at its 
end a horizontal ring of iron in which is fixed 
a heavy glass tube supporting a cup of polished 
iron which is insulated from the column (Fig. 
132). 

This cup has at its lower part a small pocket 
of lamb-skin or of India rubber, which by 
means^ of a screw beneath may be raised or lowered. This 
flexible bottom allows the operator to lower or raise at will the 
level of the mercury introduced afterwards into the iron cup. 
Another lateral screw permits connection to be made with the 
negative electrode. 3. A cast-iron beam carrying in the mid- 
dle two sharp knife-edges of the best steel hardened and 
polished. At each extremity there are two parallel bearings 
of steel separated by a notch, and intended for the knife-edges 
of the scale-pan that receives the weights, and those of the 
frame supporting the articles to be plated. One of the arms 
of the beam is provided with a stout platinum wire, placed im- 
mediately above and in the centre of the cup of mercury. 
According as the beam inclines one way or the other, this wire 




314 



ELECTRO-DEPOSITION OF METALS. 



plays in or out of the cup. 4. A scale-pan for weights, with 
two knife-edges of cast-steel, which is attached to four chains 
supporting a wooden pan for the reception of weights. A 
smaller pan above is intended for the weights corresponding to 
that of the silver to be deposited. 5. The frame for support- 
ing the articles to be plated, which is also suspended from 
two steel knife-edges, and the rod of which is formed of a stout 



Fig. 




brass tube attached below to the brass frame proper, which last 
is equal in dimensions to the opening of the vat, and supports 
the rods to which the articles are suspended. 

Fig. *33 shows a Roseleur plating balance, together with the 
resistance board, voltmeter, and silver bath ; and will be under- 
stood without further explanation. 



DEPOSITION OF SILVER. 315 

For calculating the weight of the deposit from the density of 
current, see " Chemical and Electric Equivalents," in the 
Appendix. 

When the articles have received a deposit of the required 
weight, they are treated for the prevention of subsequent yel- 
lowing according to one of the methods given on p. 306, then 
scratch- brushed with the use of decoctions of soap-root, 
plunged in hot water and dried in sawdust. 

Articles which are to retain the beautiful crystalline dead 
white with which they come from the bath are, without touch- 
ing them with the fingers or knocking them against the sides of 
the vessel, plunged into very hot clean water, and then sus- 
pended free to dry. Immediately alter drying, they are to be 
provided with a thin coat of kristalline or zapon to protect the 
dead white coating, which readily turns yellow., and, moreover, 
is very sensitive. 

The silvered articles having been scratch - brushed, must 
finally be polished, which may be effected upon a fine felt 
wheel with the use of rouge, but imparting high lustre by 
burnishing is to be preferred, the deposit being first treated 
with the steel burnisher, and then with the stone burnisher, as 
explained on p. 156. 

In some establishments in which plated table-ware in large 
quantity is turned out, ingeniously devised burnishing machines 
driven by power are in use, by which much of the manual labor 
is spared. The knife, spoon, etc., each supported by its tips 
in a suitable holder, are very slowly rotated, while the burn- 
ishing tool moves quickly over the surface, performing the 
work rapidly and satisfactorily. 

When burnishing is completed, the surface is wiped off 
longitudinally with an old, soft calico rag. Sawdust, hard cloth, 
and tissue paper produce streaks. 

B. Ordinary silver-plating. — Objects which are to receive a 
deposit of less thickness, have to undergo exactly the same 
operations described under plating by weight, the only differ- 
ence being that for quicking a weaker solution (15 to 31 grains 



3l6 ELECTRO- DEPOSITION OF METALS. 

of nitrate of mercury to I quart of water), or very dilute solution 
of potassium mercury cyanide (jy grains of potassium mercury 
cyanide and JJ grains of potassium cyanide to I quart of water) 
is used, and that the objects remain a shorter time in the bath. 
As previously mentioned, iron, steel, zinc and tin should first 
be coppered or brassed. However, tin and Britannia may also 
be directly plated, but the bath must be rich in silver and con- 
tain a large excess of potassium cyanide. Further, the current 
should be so strong that the articles acquire a blue-gray color. 
They are then suspended in the silver bath of normal composi- 
tion, and plating is finished with a normal current. 

The same process is also suitable for plating articles of Ger- 
man silver rich in nickel. In polishing such articles it is fre- 
quently observed that the deposit rises, but by plating in the 
above-mentioned preparatory bath, and finishing in the normal 
bath, the deposit will very well bear polishing with the steel. 

For silver-plating Britannia ware and articles of tin, Gore 
recommends the following process : Boil the articles in caustic 
potash solution, scratch-brush them, and plate them prepara- 
tively with a strong current and the use of large anode-surfaces 
in a hot silver bath (194 F.), and then finish deposition to 
the desired thickness in the ordinary cold silver bath. 

According to an Australian patent, the following process is 
claimed to yield good results in directly silver plating iron and 
steel. The article to be plated having first been dipped in hot 
dilute hydrochloric acid, is brought into solution of mercury 
nitrate, and then connected with the zinc pole of a Bunsen ele- 
ment. It becomes quickly coated with a layer of mercury, 
when it is taken out, washed and brought into an ordinary sil- 
ver bath. When covered with a layer of silver of sufficient 
thickness, it is heated to 572 F., the mercury evaporating at 
this temperature. It is claimed that silver deposited in this 
manner adheres more firmly than by any other process, but it 
is doubtful whether for solid silver-plating this method can re- 
place previous coppering. 

According to Dr. William H. Wahl, in the United States the 



DEPOSITION OF SILVER. 317 

practice of previous coppering is not adopted either with Bri- 
tannia metal or steel. The practice of different establishments 
in cleansing their work differs somewhat, but all aim at the 
same results, viz., to secure a smooth adhering coating of metal 
upon an inferior base. 

The practice of the Meriden Britannia Co. 's works at Meriden, 
Conn., as observed by Dr. William H. Wahl, is substantially as 
follows : 

With Britannia or "white metal:" The article is first 
cleansed of all grease by immersion in boiling alkali ; then into 
dilute hydrochloric acid ; then into a " striking" solution, viz., a 
weak cyanide of silver solution with a large proportion of free 
cyanide of potassium, and a large silver anode operated with a 
very strong electric current. The purpose of immersion in this 
solution is to effect an instantaneous deposit of silver on the 
metal, to better insure a perfect coating in the silver bath 
proper. The articles remain in the " striking" solution for a 
few seconds only, as its action, owing to the large proportion 
of free cyanide it contains, is very prompt, and as soon as they 
have received a thin coating, which takes place almost imme- 
diately, they are removed to the electro-plating bath, where 
they remain until they have received the proper coating of 
silver. In many cases, especially with articles of considerable 
size, cleansing in boiling alkali must be supplemented by 
scratch-brushing, in which case the acid dip may be dispensed 
with, and the article, after thorough rinsing and dipping in 
alkali to remove finger-marks, is immersed at once in the 
"striking" solution. 

German silver or nickel articles are first cleansed in boiling 
alkali, washed, then dipped in a mixture of two-thirds sulphuric 
acid and one-third nitric acid, then into quicking solution, then 
into the " striking" solution, and from this into the plating bath. 

Steel articles are cleansed in boiling alkali, rinsed, dipped in 
hydrcchloric acid, then in the " striking" solution, and from this 
into the plating bath. In case the articles require scouring, 
the acid dip is dispensed with. For steel two "striking" solu- 



318 ELECTRO-DEPOSITION OF METALS. 

tions are used, one somewhat richer in silver than the other, 
the weaker solution being used first. 

With the William Rogers Manufacturing Co., Hartford, 
Conn., the following is the general outline of the methods in 
use for preparing work for plating : — 

For cleansing (steel) cutlery. — Immersion in boiling alkali for 
the removal of grease; scouring; rinsing; dipping into strong 
hydrochloric acid ; then for a few seconds in a silver " striking " 
solution; then in a plating bath until the required amount of 
silver is deposited. 

The formula for the " striking " solution, which will be given 
later on, is low in silver, rich in cyanide, and worked with a 
strong current and silver anode. 

Nickel-silver (German silver) for spoons. — Immerse in boil- 
ing alkali; scouring, if necessary rinsing in water; immersion 
in acid mixture, composed of two-thirds sulphuric acid and 
one-third nitric acid; dipping in weak quicking solution (either 
very dilute potassium-mercury cyanide or acidulated nitrate of 
mercury) ; immersion for a few seconds in the silver " striking" 
solution ; and from this into the plating bath. 

Britannia metal ( hollow-ware'). — Cleansing in alkali as above ; 
rinsing in water; again immersing in alkali to remove finger- 
marks, if necessary, immersing in the " striking" solution, and 
from this into the plating solution. A quicking solution for 
Britannia, sometimes employed, is composed of a strong solu- 
tion of sal ammoniac and corrosive sublimate, into which the 
articles are dipped after cleansing in potash. 

The silver " striking" solution, as used by the Wm. Rogers 
Manufacturing Co., of Hartford, Conn., is composed as follows: 

Rogers s "striking" solution. — Cyanide of potassium, 6 ozs. ; 
silver, y 2 oz. ; water, I gallon. Use a strong current. 

Meriden Company's "striking solution!' — Cyanide of potas- 
sium, 12 to 16 ozs.; silver, 8 to io dwt. ; water, I gallon. 

The plating solution commonly employed by the Wm. 
Rogers Manufacturing Co., has the following composition: 
Cyanide of potassium, 6 ozs,; silver (in chlorate), 4 ozs.; 
water, 1 gallon. 



DEPOSITION OF SILVER. 319 

The usual formula of the Meriden Britannia Co., has the fol- 
lowing proportions: Cyanide of potassium, 12 ozs. ; silver, 
3 ozs. ; water, 1 gallon. 

In order to secure an extra heavy coating of silver on the 
convex surfaces of spoons and forks, which, being subject to 
greater wear than the other parts, require extra protection, the 
Meriden Britannia Co. uses a frame in which the articles sup- 
ported therein by their tips are placed horizontally in a shallow 
silver bath, and immersed just deep enough to allow the pro- 
jecting convexities to dip into the bath. By this artifice these 
portions are given a second coating of silver of any desired 
thickness. This mode of procedure, which is termed " sec- 
tional" plating, accomplishes the intended purpose nicely and 
satisfactorily. In some establishments the silvered forks and 
spoons are placed between plates of gutta-percha of corre- 
sponding shape, and held together by rubber bands. In these 
plates the portions to be provided with an extra coating of 
silver are cut out. By suspending the forks and spoons thus 
protected in the bath, the unprotected places receive a further 
layer of silver, the outlines of which are later on smoothed 
down with burnishers. The second object may also be 
attained by coating the places which are to receive no further 
deposit with " stopping-off" varnish (see below). 

Stopping off. — If certain parts of a metallic article are not to 
receive a deposit, as for instance, when a contrast is to be 
effected by depositing different metals upon the same object, 
these parts are covered or " stopped-off," with a varnish. 
Stopping-off varnish is prepared by dissolving asphalt or dam- 
mar with an addition of mastic in oil of turpentine. Apply 
with a brush, and after thoroughly drying the articles in the 
drying-chamber, place them for an hour in very cold water, 
whereby the varnish hardens completely. After plating, the 
varnish is removed, best with benzine, the article plunged in 
hot water, and dried in saw-dust. 

For a varnish that will resist the solvent power of the hot 
alkaline gilding liquid, Gore recommends the following compo- 



320 ELECTRO-DEPOSITION OF METALS. 

sition : Translucent rosin 10 parts, yellow beeswax 6, extra- 
fine red sealing-wax 4, finest polishing rouge 3. 

Quick-drying stopping-off varnishes, which harden immedi- 
diately at the ordinary temperature, and resist cyanide baths, 
are now found in commerce. 

Silvering by contact, by immersion, and cold stirring with 
paste. — For silvering by contact with zinc, the bath prepared 
according to formula II, may be used, adding about 17 grains 
more of potassium cyanide per quart. The articles are to be 
prepared in the same manner as for plating by weight, and 
quicked in a weak quicking solution. Before placing the arti- 
cles in the bath they are wrapped round with bright zinc wire, 
or are brought in contact while in the bath with a bright strip 
of zinc, care being had to frequently change the points of con- 
tact to prevent the formation of stains. As previously men- 
ioned, by the contact of the metal to be silvered with the 
electro-positive zinc, a weak current is produced which effects 
the deposition of the silver ; but as this takes place very slowly, 
it is best to heat the silver bath. Silver being at the same time 
deposited upon the zinc, the latter must be frequently freed 
from the deposit and brightened by means of a file or emery 
paper. 

By contact with zinc, silver may also be deposited in one of 
the following baths for silvering by immersion. 

Crystallized nitrate of silver 5.64 drachms, 98 per cent, po- 
tassium cyanide 1.23 ozs., distilled water 1 quart. To prepare 
the bath dissolve the silver salt in 1 pint of the water, then the 
potassium cyanide in the remaining pint of water, and mix the 
two solutions. The bath is heated in a porcelain or enameled 
iron vessel to between 176 and 194 F., and the thoroughly 
cleansed and pickled objects are immersed in it until uniformly 
coated, previous quicking being not required. The deposit is 
lustrous if the articles are left but a short time in the bath, but 
becomes dull when they remain longer. In the first case the 
deposit is a mere film, and, while it is somewhat thicker in the 
latter, it can under no circumstances be called solid. 



DEPOSITION OF SILVER. 



321 



The bath gradually works less effectively and finally ceases 
to silver, when its action may be restored by the addition of 
2^ to ^ Y / 2 drachms of potassium cyanide per quart. Should 
this prove ineffectual, the content of silver is nearly exhausted, 
and the bath is evaporated to dryness, and the residue added 
to the silver waste. Frequent refreshing of the bath with silver 
salt cannot be recommended, the silvering always turning out 
best in a fresh bath. 

A solution of nitrate of silver in sodium sulphide is, accord- 
ing to Roseleur, very suitable for silvering by immersion. The 

Fig. 134. 




solution is prepared by pouring into a moderately concentrated 
solution of sodium sulphide, while constantly stirring, solution 
of a silver salt until the precipitate of silver sulphide formed 
begins to be dissolved with difficulty. This bath can be used 
cold or warm, fresh solution of silver being added when it com- 
mences to lose its effect. If, however, the bath is not capable 
of dissolving the silver sulphide formed, concentrated solution 
of sodium sulphide has to be added. 

For the preparation of the solution of sodium sulphide, 
Roseleur recommends the following method : — 

Into a tall vessel of glass or porcelain (Fig. 134) introduce 5 

21 



322 ELECTRO-DEPOSITION OF METALS. 

quarts of water and 4 pounds of crystallized soda, after pour- 
ing in mercury about an inch or so deep to prevent the glass 
tube through which the sulphurous acid is introduced from 
being stopped up by crystals. The sulphurous acid is evolved 
by heating copper turnings with concentrated sulphuric acid, 
washing the gas in a Woulff bottle filled an inch or so deep 
with water, and introducing it into the bottle containing the 
soda solution, as shown in the illustration. A part of the soda 
becomes transformed into sodium sulphide, which dissolves, 
and a part is precipitated as carbonate. The latter, however, 
is transformed into sodium sulphide by the continuous action 
of sulphurous acid, and carbonic acid gas escapes with efferves- 
cence. When all has become dissolved, the introduction of 
sulphurous acid should be continued until the liquid slightly 
reddens blue litmus paper, when it is set aside for 24 hours. 
At the end of that time a certain quantity of crystals will be 
found upon the mercury, and the liquid above, more or less 
colored, constitutes the sodium sulphide of the silvering bath. 
The liquid sodium sulphide thus prepared should be stirred 
with a glass rod, to eliminate the carbonic acid which may still 
remain in it. The liquid should then be again tested with blue 
litmus paper; and if the latter is strongly reddened, carbonate 
of soda is cautiously added, little by little, in order to neutralize 
the excess of sulphurous acid. On the other hand, if red litmus 
paper becomes blue, too much alkali is present, and more 
sulphurous acid gas must be passed through the liquid, which 
is in the best condition for our work when it turns litmus-paper 
violet or slightly red. The solution should mark from 22 to 
26 Be., and should not come in contact with iron, zinc, tin, or 
lead. 

As will be seen, this mode of preparing the sodium sulphide 
solution is somewhat troublesome, and it is therefore recom- 
mended to proceed as follows : Prepare a saturated solution of 
commercial sodium sulphide. The solution will show an alka- 
line reaction, the commercial salt frequently containing some 
sodium carbonate. To this solution add, while stirring, solu- 



DEPOSITION OF SILVER. 323 

tion of bisulphide of sodium saturated at 122 F., until blue 
litmus paper is slightly reddened. Then add to this solution 
concentrated solution of nitrate of silver until the flakes of sil- 
ver sulphide separated begin to dissolve with difficulty. 

The immersion-bath, prepared according to one or the other 
method, works well, the silvering produced having a beautiful 
lustre, such as is desirable for many cheap articles. If the 
articles are allowed to remain for a longer time in the bath, a 
matt deposit is obtained. For bright-silvering, the bath should 
always be used cold. It must further be protected as much as 
possible from the light, otherwise gradual decomposition takes 
place. 

According to Dr. Ebermayer, a silver-immersion bath for 
bright silvering is prepared as follows : Dissolve 1.12 ozs. of 
nitrate of silver in water, and precipitate the solution with 
caustic potash. Thoroughly wash the silver oxide which is 
precipitated, and dissolve it in 1 quart of water which contains 
3.52 ozs. of potassium cyanide in solution, and finally dilute the 
whole with one quart more water. For silvering, the bath is 
heated to the boiling point, and the silver withdrawn may be 
replaced by the addition of moist silver oxide as long as com- 
plete solution takes place. When the silvering is no longer 
beautiful and of a pure white color, the bath is useless, and is 
then evaporated. Experiments with a bath prepared according 
to the above directions were not satisfactory, the coating being 
dull and adhering badly. 

For silvering articles, especially those composed of the vari- 
ous alloys of copper, without the use of a current, the following 
process is recommended in " Edelmetallindustrie." Dissolve 
silver in nitric acid with the assistance of the sand or water 
bath, and convert it into chloride of silver by carefully adding 
hydrochloric acid or common salt solution until, after repeated 
stirring and allowing to settle, no more precipitate is formed. 
Now let the mixture repose, then pour off the supernatant fluid 
and wash the white caseous precipitate until litmus-paper is no 
longer reddened by the wash-water. Keep the chloride of silver 



324 ELECTRO-DEPOSITION OF METALS. 

thus obtained in wide-mouthed black bottles. Now prepare 
in glazed pots two baths as follows: I. A potassium- cyanide 
bath by dissolving 1 1 J^ drachms of chloride of silver and 2 ozs. 
of potassium cyanide in about io quarts of water, and heating 
the mixture to the boiling point. 2. A salt bath consisting of 
io quarts of water, n lbs. of common salt, n lbs. of cream of 
tartar, and 4^ ozs. of chloride of silver. Boil the mixture, 
with constant stirring, for one hour, and when cold pour it into 
another pot, in which it may be kept. The articles to be 
silvered are cleansed by treating them with dilute hydrochloric 
acid. They are next pickled by dipping them in nitric acid, 
and finally plunged into a bright- dipping bath, consisting of 
nitric acid, a small quantity of hydrochloric acid and a trace of 
lamp-black. They are then thoroughly rinsed off, and thrown 
into water containing a small quantity of cream of tartar, where 
they remain until they are silvered. The water must not be 
warm and the articles should not remain in it too long, other- 
wise they will tarnish and it will be impossible to obtain a pure 
silvering. The articles thus prepared are first brought into the 
potassium-cyanide bath and gently agitated, when they become 
immediately coated with a thin film of silver. They are then 
rinsed and brought into a dilute salt bath, prepared by adding 
water to a portion of the salt given under 2, where they remain 
until they have acquired a gray-white or yellowish-white color. 
They are then rinsed, returned to the potassium-cyanide bath, 
again rinsed and thrown into clean water, or dried in sawdust. 
Each rinsing must be effected in a different vessel. The two 
baths are very lasting, and require only a periodical addition of 
potassium cyanide (when the articles on being immersed be- 
come black, which turns slowly to white), or of chloride of sil- 
ver (when the articles show r a yellowish- white color). When 
the dilute salt bath becomes too weak, a fresh quantity of the 
salt bath is added by means of a wooden spoon. The potas- 
sium-cyanide bath must every day be agitated. During the 
process of silvering the potassium- cyanide bath is to be kept 
at between 176 and 194 F., and the salt bath at above 21 2° 



DEPOSITION OF SILVER. 325 

F. The potassium-cyanide bath should only be boiled before 
use, when making a fresh addition of potassium cyanide, or of 
chloride of silver. The silvering obtained is pure white, cheap 
and durable. 

The process of coating with a thin film, or rather whitening 
with silver, small articles, such as hooks and eyes, pins, etc., 
differs from the above-described immersion method, which 
affects the silvering in a few seconds, in that the articles require 
to be boiled for a longer time. The process is as follows: 
Prepare a paste from 14.11 drachms of nitrate of silver, pre- 
cipitated as chloride of silver; 44 ounces of cream of tartar, 
and a like quantity of common salt, by precipitating the solu- 
tion of the nitrate of silver with hydrochloric acid, washing the 
chloride of silver and mixing it with the above-mentioned 
quantities of cream of tartar and common salt, and sufficient 
water to a paste, which is kept in a dark glass vessel to prevent 
the chloride of silver from being decomposed by the light. 
Small articles of copper or brass are first freed from grease, and 
pickled. Then heat in an enameled kettle 3 to 5 quarts of 
rain-water to the boiling point; add 2 or 3 heaping teaspoon- 
fuls of the above-mentioned paste, and bring the metallic 
objects contained in a stoneware sieve into the bath and stir 
them diligently with a rod of glass or wood. Before placing a 
fresh lot of articles in the bath additional silver paste must be 
added. If finally the bath acquires a greenish color, caused by 
dissolved copper, it is no. longer suitable for the purpose, and is 
then evaporated and added to the silver residues. 

Cold silvering with paste. — In this process an argentiferous 
paste, composed as given below, is rubbed, by means of the 
thumb, a piece of soft leather or rag, upon the cleansed and 
pickled metallic surface (copper, brass, or other alloys of 
copper) until it is entirely silvered. The paste may also be 
rubbed in a mortar with some water to a uniform thinly-fluid 
mass, and applied with a brush to the surface to be silvered. 
By allowing the paste to dry naturally, or with the aid of a 
gentle heat, the silvering appears. The application of the paste 



326 ELECTRO-DEPOSITION OF METALS. 

by means of a brush is chiefly made use of for decorating with 
silver, articles thinly gilded by immersion. For articles not 
gilded, the above-mentioned rubbing on of the stiff paste is to 
be preferred. 

Composition of argentiferous paste. — I. Silver in the form of 
freshly precipitated chloride of silver,* 0.35 oz. common salt 
0.35 oz., potash 0.7 oz., whiting 0.52 oz., and water a sufficient 
quantity to form the ingredients into a stiff paste. 

II. Silvering in the form of freshly precipitated chloride of 
silver* 0.35 oz., potassium cyanide 1.05 ozs., sufficient water to 
dissolve these two ingredients to a clear solution, and enough 
whiting to form the whole into a stiff paste. This paste is 
also excellent for polishing tarnished silver; it is, however, 
poisonous. 

The following non-poisonous composition does excellent ser- 
vice : Silver in the form of chloride of silver 0.35 oz., cream of 
tartar 0.7 oz., common salt 0.7 oz., and sufficient water to form 
the mixture of the ingredients into a stiff paste. 

Another composition is as follows : Chloride of silver 1 part, 
pearl-ash 3, common salt 1*4, whiting 1, and sufficient water to 
form a paste. Apply the latter to the metal to be silvered and 
rub with a piece of soft leather. When the metal is silvered, 
wash in water to which a small quantity of washing soda has 
been added. 

Graining. — In gilding parts of watches, gold is seldom di- 
rectly applied upon the copper ; there is generally a preliminary 
operation called graining, by which a grained and slightly dead 
appearance is given to the articles. Marks of the file are ob- 
literated by rubbing upon a whetstone, and lastly upon an oil- 
stone. Any oil or grease is removed by boiling the parts for a 
few minutes in a solution of 10 parts of caustic soda or potash 
in 100 of water, which should wet them entirely if all the oil 
has been removed. The articles being threaded upon a brass 
wire, cleanse them rapidly in the acid mixture for a bright 

* From 0.56 oz. of nitrate of silver. 



DEPOSITION OF SILVER. 327 

lustre, and dry them carefully in white wood sawdust. The 
pieces are fastened upon the even side of a block of cork by 
brass pins with flat heads. The parts are then thoroughly 
rubbed over with a brush entirely free from grease, and dipped 
into a paste of water and very fine pumice-stone powder. 
Move the brush in circles, in order not to rub one side more 
than the other; thoroughly rinse in cold water, and no particle 
of pumice-stone should remain upon the pieces or the cork. 
Next place the cork and the pieces in a weak mercurial solu- 
tion, composed of water 2*^ gallons, nitrate or binoxide of 
mercury ^t oz -> sulphuric acid \ oz., which slightly whitens the 
copper. The pieces are passed quickly through the solution 
and then rinsed. This operation gives strength to the grain- 
ing, which without it possesses no adherence. 

The following preparations may be used for graining: I. 
Silver in impalpable powder 2 ozs., finely pulverized cream of 
tartar 20 ozs.. common salt 4 lbs. II. Silver powder 1 oz.* 
cream of tartar 4 to 5 ozs., common salt 13 ozs. III. Silver 
powder, common salt, and cream of tartar, equal parts by 
weight of each. The mixture of the three ingredients must be 
thorough and effected at a moderate and protracted heat. The 
graining is the coarser the more common salt there is in the 
mixture, and it is the finer and more condensed as the propor- 
tion of cream of tartar is greater, but it is then more difficult to 
scratch-brush. The silver powder is obtained as follows : Dis- 
solve in a glass or porcelain vessel J^ oz. of crystallized nitrate 
of silver in 2^ gallons of distilled water, and place 5 or 6 
ribands of cleansed copper, ^ inch wide, in the solution. 
These ribands should be long enough to allow of a portion of 
them being above the liquid. The whole is kept in a dark 
place, and from time to time stirred with the copper ribands. 
This motion is sufficient to loosen the deposited silver, and 
present fresh surfaces to the action of the liquor. When no 
more silver deposits on the copper the operation is complete, 
and there remains a blue solution of nitrate of copper. The 
silver powder is washed by decantation or upon a filter until 
there remains nothing of the copper solution. 



328 ELECTRO-DEPOSITION OF METALS. 

For the purpose of graining, a thin paste is made of one of 
the above mixtures and water, and spread by means of a spatula 
upon the watch parts held upon the cork. The cork itself is 
placed upon an earthenware dish, to which a rotating move- 
ment is imparted by the left hand. An oval brush with close 
bristles, held in the right hand, rubs the watch parts in every 
direction, but always with a rotary motion. A new quantity of 
paste is added two or three times and rubbed in the manner in- 
dicated. The more the brush and cork are turned the rounder 
becomes the grain, which is a good quality, and the more paste 
added the larger the grain. When the desired grain is obtained 
the pieces are washed and scratch-brushed. The brushes em- 
ployed are of brass wire, as fine as hair, and very stiff and 
springy. It is necessary to anneal them upon an even fire to 
different degrees ; one soft or half annealed for the first opera- 
tion or uncovering the grain ; one harder for bringing up the 
lustre ; and one very soft or fully annealed, used before gilding 
for removing any marks which may have been made by the 
preceding tool, and for scratch-brushing after gilding, which, 
like the graining, must be done by giving a rotary motion to 
the tool. If it happens that the same watch part is composed 
of copper and steel, the latter metal requires to be preserved 
against the action of the cleansing acids and of the graining 
mixture by a composition called resist. This consists in cover- 
ing the pinions and other steel parts with a fatty composition 
which is sufficiently hard to resist the tearing action of the 
bristle and wire brushes, and insoluble in the alkalies of the gild- 
ing bath. A good composition is : Yellow wax, 2 parts by 
weight; translucent rosin, 3^ ; extra fine red sealing-wax, 1 J^ ; 
polishing rouge, 1. Melt the rosin and sealing-wax in a porce- 
lain dish, upon a water-bath, and afterwards add the yellow wax. 
When the whole is thoroughly fluid, gradually add the rouge 
and stir with a wooden or glass rod. Wifhdraw the heat, but 
continue the stirring until the mixture becomes solid, otherwise 
all the rouge will fall to the bottom. The flat parts to receive 
this resist are slightly heated, and then covered with the mix- 



DEPOSITION OF SILVER. 329 

ture, which melts and is easily spread. For covering steel 
pinions employ a small gouge of copper or brass fixed to a 
wooden handle. The metallic part of the gouge is heated upon 
an alcohol lamp and a small quantity of resist is taken with it. 
The composition soon melts, and by turning the tool around 
the steel pinion thus becomes coaled. Use a scrateh-brush 
with long wires, as their flexibility prevents the removal of the 
composition. When the resist is to be removed after gilding, 
put the parts into warm oil or tepid turpentine, then into a very 
hot soap-water or alkaline solution ; and, lastly, into fresh water. 
Scratch-brush and dry in warm, white wood sawdust. The 
holes of the pinions are cleansed and polished with small pieces 
of very white, soft wood, the. friction of which is sufficient to 
restore the primitive lustre. The gilding of parts of copper and 
steel requires the greatest care, as the slightest rust destroys 
their future usefulness. Should some gold deposit upon the 
steel, it should be removed by rubbing with a piece of wood 
and impalpable pumice dust, tin-putty, or rouge. 

The gilding of the grained watch parts is effected in a bath 
prepared according to formula I. or III., given under " Deposi- 
tion of Gold." 

Silvering of fine copper wire is effected in an apparatus similar 
to that shown in Fig. 125, p. 239, a reservoir containing potas- 
sium cyanide solution for pickling the cleansed wire being 
added and placed in front of the silver bath. Lustre is im- 
parted to the silvered wire by drawing through a draw-plate. 
Further details will be found under " Deposition of Gold." 

Incrustations with silver, gold, and other metals. — By incrust- 
ing is understood the inlaying of depressions, produced by en- 
graving or etching upon a metallic body, with silver, gold, and 
other metals, such as Japanese incrustations, which are made 
by mechanically pressing the silver or gold into the depres- 
sions. Such incrustations, however, can also be produced by 
electro-deposition, the process being as follows : The design 
which is to be incrusted upon a metal is executed with a pig- 
ment of white-lead and glue-water or gum-water. The portion 



330 ELECTRO-DEPOSITION OF METALS. 

not covered by the design is then coated with stopping-off 
varnish. The article is next placed in dilute nitric acid, 
whereby the pigment is first dissolved, and next the surface 
etched, which is allowed to progress to a certain depth. 
Etching being finished, the article is washed in an abundance 
of water and immediately brought into a silver or gold bath, 
in which, by the action of the current, the exposed places are 
filled up with metal. This being done, the "stopping-off" 
varnish is removed with benzine, the surface ground smooth,, 
and polished. In this manner one article may be incrusted 
with several metals; for instance, brass may be incrusted with 
copper, silver, and gold, and by oxidizing or coloring portions- 
of the copper beautiful effects can be produced. The principal 
requisites for these incrustations are manual skill and much 
patience. Expensive apparatus is not required, every skilled 
electro-plater being able to execute the work. 

Imitation of niel or nielled silvering.— -By nielling is under- 
stood the inlaying of designs produced either by engraving or 
stamping, with a black mixture of metallic sulphides. The 
nielling powder is prepared by melting, silver 20 parts by weight, 
copper 90 parts, and lead 1 50 parts. To the liquid metallic 
mass add 26^ ozs. of sulphur and ^ oz. of sal ammoniac, 
quickly cover the crucible, and continue heating until the excess 
of sulphur is volatilized. Then pour the contents of the cruci- 
ble into another crucible, the bottom of which is covered about 
Y^ inch deep with flowers of sulphur, cover the crucible and allow 
the mixture to cool. When cold bring the contents once more 
to the fusing point, and pour the fused mass in a thin stream 
into a bucket filled with water, whereby granulated metal is 
formed, which can be readily reduced in a mortar to a fine 
powder. This powder is mixed with sal ammoniac and gum- 
water to a thin paste. This paste is brought into the designs 
produced by engraving or stamping, and after drying burnt 
in a muffle. When cold any roughness is removed by grinding, 
and after polishing a sharp black design in white silver is 
obtained. 



DEPOSITION OF SILVER. 33 I 

To imitate niel by electro deposition, the design is executed 
upon the surface with a pigment consisting of white lead and 
glue or gum-water. The portions which are to remain free are 
coated with " stopping-off" varnish, and the design is uncovered 
by etching with very dilute nitric acid. The article is then 
brought as the anode into dilute solution of ammonium sul- 
phide, while a small sheet of platinum connected to the nega- 
tive pole is dipped into the solution. Sulphide of silver being 
formed, the design becomes rapidly black gray, and after re- 
moving the " stopping-ofT" varnish with benzine, stands out in 
sharp contrast from the white silver. 

Upon brass, nielling may be imitated by silvering the article 
and then engraving the design, by which the silver is removed 
and the brass uncovered. The article is then brought into the 
black bright dip, by which the uncovered brass is colored black 
while the silvered portions remain unchanged. If portions in 
relief are to be made black, the silvering is removed by grind- 
ing, the article dipped into cream of tartar solution and then 
brought into the black bright dip. This process is largely em- 
ployed by manufacturers of buttons when silvered buttons are 
to be supplied with the name of the firm and the quality number 
in black. 

Old {antique) silvering. — To give silvered articles an antique 
appearance coat them with a thin paste of 6 parts graphite, I 
red ochre, and sufficient spirits of turpentine. After drying, 
gentle rubbing with a soft brush removes the excess of powder, 
and the reliefs are set off (discharged) by means of a rag 
dipped into alcohol. 

A tone resembling antique silvering is also obtained by brush- 
ing the silvered articles with a soft brush moistened with very 
dilute alcoholic solution of chloride of platinum. 

In order to impart the old silver tinge to small articles, such 
as buttons, rings, etc., they are agitated in the above-mentioned 
paste, and then " tumbled" with a large quantity of dry saw- 
dust until the desired shade is obtained. 

Many operators, at the present day, produce the antique 



332 ELECTRO-DEPOSITION OF METALS. 

silvering by beginning with the oxidizing process described 
below, and setting off the reliefs by means of a hard brush 
and pumice-stone, or Spanish white. The last process is 
almost exclusively used for metallic mountings of books and 
albums. 

With the use of the electric current and carbon anodes, 
antique silver may be produced as follows : Bring the silvered 
articles, previously thoroughly freed from grease, into the old 
silver bath at a current-tension of 4 to 5 volts, and allow them 
to remain for a few minutes until they become covered with a 
uniform blue-gray deposit. They are then thoroughly rinsed 
in water, and the raised portions rubbed with very fine pumice, 
to lay bare the silver. If surfaces are to appear in antique sil- 
ver, the deposit is only sufficiently removed with pumice for 
the silver to shine through, and the surface to show the proper 
antique silver tone. 

Oxidized silver. — This term is incorrect, as by it is under- 
stood not an oxidation, but a combination with sulphur or 
chlorine. Solution of pentasulphide of potassium (liver of 
sulphur of the shops) is generally used for the purpose. Im- 
merse the articles in a solution of 2.75 drachms of liver of 
sulphur and 5^ drachms of ammonium carbonate in 1 quart 
of water heated to 176 F., and allow them to remain until they 
have acquired the desired dark tone. Immediately after im- 
mersion, the articles become pale gray, then darker, and finally, 
deep black-blue. For coloring in this manner, the silvering 
should not be too thin. For articles with a very thick deposit 
of silver, solution of double the strength may be used. Very 
slightly silvered articles cannot be oxidized in this manner, as 
the bath would remove the silvering, or under the most favor- 
able circumstances produce only a gray color. If the operation 
is not successful, and the articles come from the bath stained, 
or otherwise defective, dip them in a warm potassium cyanide 
solution, which rapidly dissolves the silver sulphide formed. 

A yellow color is imparted to silvered articles by immersion 
in a hot concentrated solution of chloride of copper, rinsing 
and drying. 



DEPOSITION OF SILVER. 333 

Stripping silvered articles. — When a silvering operation has 
failed, or the silver is to be stripped from old silvered articles, 
different methods have to be used according to the nature of 
the basis -metal. Silvered iron articles are treated as the anode 
in potassium cyanide solution in water (i : 20), the iron not 
being attacked by potassium cyanide. As cathode suspend 
in the solution a few silver anodes or a copper sheet rubbed 
with an oily rag; the silver precipitates upon the copper 
sheet, but does not adhere to it. Articles, the basis of 
which is copper, are best stripped by immersion in a mixture of 
equal parts of anhydrous (fuming) sulphuric acid and nitric 
acid of 40 Be. This mixture makes the copper passive, it 
not being attacked while the silver is dissolved. Care must, 
however, be had not to introduce any water into the acids, nor 
to let them stand without being hermetically closed, since by 
absorbing moisture from the air they become dilute, and may 
then exert a dissolving effect upon the copper. The fuming 
sulphuric acid may also be heated in a shallow pan of enam- 
eled cast iron to between 300 and 400 F. Then, at the 
moment of using it, pinches of dry and pulverized nitrate of 
potassium (saltpetre) are thrown into it, and the article, held 
with copper tongs, is plunged into the liquid. The silver is 
rapidly removed, while the copper or its alloys is but slightly 
corroded. According to the rapidity of the solution, fresh ad- 
ditions of saltpetre are made. All the silver has been dissolved 
when, after rinsing in water and dipping the articles into the 
cleansing acids, they present no brown or black spots, that is 
to say, when they behave like new, In this hot acid stripping 
proceeds more quickly than in the cold acid mixture, but the 
latter acts more uniformly. 

Determination of silver-plating. — By applying to genuine 
silver-plating a drop of nitric acid of 1.2 specific gravity, in 
which red chromate of potash has been dissolved to saturation, 
a red stain of chromate of silver is formed. According to 
Grager, this method may also be used, to a certain extent, for 
the recognition of other white metal which may be mistaken 



334 ELECTRO-DEPOSITION OF METALS. 

for silver. A drop of the mixture applied to German silver be- 
comes brown, no red stain appearing after rinsing with water; 
upon Britannia the drop produces a black stain ; zinc is etched 
without a colored spot remaining behind ; upon amalgamated 
metals a brownish precipitate is formed, which does not adhere 
and is washed away by water; upon tin the drop also acquires 
a brownish color, and by diluting with water a yellow precipi- 
tate is formed ; upon lead a beautiful yellow precipitate is 
formed. 

Custom-house officers in Germany are directed by law to use 
the following process for the determination of genuine silver- 
plating : Wash a place on the article with ether or alcohol, dry 
with blotting paper, and apply to the spot thus cleansed a drop 
of a I to 2 per cent, solution of crystallized bisulphite of soda 
prepared by boiling 1.05 ozs. of sodium sulphite and 2.36 
drachms of flowers of sulphur with 0.88 oz. of water until the 
sulphur is dissolved, and diluting to 1 quart of fluid. Allow 
the drop to remain upon the article about ten minutes and then 
rinse off with water. Upon silver articles, a full, round, steel- 
gray spot is produced. Other white metals and alloys, with 
the exception of amalgamated copper, do not show this phe- 
nomenon, there appearing at the utmost a dark ring at the edge 
of the drop. Amalgamated copper is more quickly colored, 
and acquires a more dead-black color than silver. 

Examination of Silver Baths. 

For the quantitative examination of silver baths, the determi- 
nation of the content of free potassium cyanide and of metallic 
silver as well as of the potassium carbonate which is formed by 
the action of air, etc., upon the potassium cyanide, has to be 
taken into consideration. 

Regarding the determination of the free potassium cyanide, 
the reader is referred to the method given under " Examination 
of copper baths containing potassium cyanide," and what has 
been said there in reference to replacing the deficiency also 
applies here. 



DEPOSITION OF SILVER. 335 

The potassium carbonate which is formed in constantly 
increasing quantities in the bath is best removed by the addi- 
tion of barium cyanide solution, whereby, in consequence of 
reciprocal decomposition, potassium cyanide is formed, while 
barium carbonate in an insoluble state is separated. 

The determination of the potassium carbonate present in the 
bath is desirable, so as to be able, on the one hand, to calculate 
the quantity of barium cyanide required for its decomposition 
and, on the other, to become acquainted with the quantity of 
free potassium cyanide formed thereby. 

The determination of the potassium carbonate is effected as 
follows : Bring by means of the pipette 20 cubic centimeters 
of the bath into a beaker, dilute with 50 cubic centimeters of 
water and compound with barium nitrate solution in excess. 
Allow to settle for some time, then filter through not too large 
a paper filter, taking care that the entire precipitate reaches 
the filter, and wash the filter thoroughly with water until a few 
drops of the filtrate, when evaporated upon a platinum sheet, 
leave no residue. Now take the filter, together with the resi- 
due, carefully from the funnel, bring it into a beaker, and add 
water, as well as a carefully measured quantity of standard 
nitric acid, which should, however, be somewhat larger than 
required for dissolving the barium carbonate. While solution 
is being effected, keep the beaker covered with a watch glass, 
and then rinse any drops appearing upon the latter into the 
beaker by means of distilled water. Add to the solution, as an 
indicator, a few drops of methyl-orange, whereby the solution 
is colored red, and add, while stirring constantly, from a 
burette, standard soda solution until the red color of the solu- 
tion passes into yellow. By now deducting the cubic centi- 
meters of soda solution used from the cubic centimeters of 
standard nitric acid added for the solution of the barium car- 
bonate, and multiplying the number of the remaining cubic 
centimeters of standard nitric acid by 3.45, the quantity of 
potassium carbonate in grammes per liter of silver bath is 
obtained. 



336 ELECTRO-DEPOSITION OF METALS. 

Now the quantity of barium cyanide has to be calculated 
which is required for the conversion of the quantity of potas- 
sium carbonate found into potassium cyanide with the separa- 
tion of barium carbonate. It is best to use a 20-per cent, 
barium cyanide solution, and since I gramme of potassium 
carbonate requires for conversion 1.36 grammes of barium 
cyanide, 6.80 grammes of 20 per cent, barium cyanide solution 
are necessary for the purpose, and each gramme of potassium 
cyanide yields 0.942 gramme of potassium cyanide. Hence 
for the determination of the potassium cyanide present after 
the destruction of the potassium carbonate, there has to be 
added to the potassium cyanide found by titration, the content 
of free potassium cyanide calculated from the conversion with 
barium cyanide. If this shows a deficit as compared with the 
original content, it is to be made up by adding only about one- 
half the quantity, for the same reason as given in speaking of 
the copper bath, namely, because the potassium formate, 
which is at the same time formed, performs the function of the 
potassium cyanide. 

For the determination of the silver, the electrolytic method is 
the most simple and suitable in so far as the silver bath can be 
directly used for the purpose. 

Bring by means of the pipette into the platinum dish 10 
cubic centimeters of the silver bath, or 20 cubic centimeters 
if the bath is weak, add, according to the greater or smaller 
excess of the potassium cyanide present, y 2 to 1 gramme of 
potassium cyanide dissolved in water, and dilute up to 1 ori^ 
centimeters from the edge of the dish. Heat, by means of a 
small flame, the contents of the dish to from 140° to 149 F., 
and maintain this temperature as nearly constant as possible. 
Electrolysis is effected with a current-density NDioo=o.o8 
ampere. Complete precipitation, which requires 3 to 3^ 
hours, is recognized by ammonium sulphide producing no dark 
coloration of the fluid. The dish is then washed, without in- 
terrupting the current, rinsed with alcohol and ether, dried for 
a short time at 21 2° F., and weighed. The weight of the pre- 



DEPOSITION OF SILVER. 337 

cipitate multiplied by 100 gives the content of silver in 
grammes per liter of bath. If 20 cubic centimeters of silver 
bath have been electrolyzed, multiply only by 50. 

If the analysis has shown a deficit of silver in the bath, it can 
be readily replaced. For strengthening the bath it is best to 
use pure crystallized potassium silver cyanide, which in round 
numbers contains 50 per cent, of silver. Suppose the bath 
contains per liter 2 grammes of silver less than it should, then 
for each liter of bath (52 : 100=2 : x ; x = 3.8 grammes), 3.8 
grammes of pure crystallized potassium silver cyanide have to 
be added. 

The more troublesome volumetric analysis may be omitted, 
it offering no advantage over the electrolytic method. 

Recovery of silver from old silver baths, etc. — Old solutions 
which contain silver in the form of a silver salt are easily treated. 
It is sufficient to add to them, in excess, a solution of common 
salt, or hydrochloric acid, when all the silver will be precipi- 
tated in the state of chloride of silver, which, after washing, may 
be employed for the preparation of new baths. 

For the recovery of silver from solutions which contain it as 
cyanide, the solutions may be evaporated to dryness, the resi- 
due mixed with a small quantity of calcined soda and potassium 
cyanide, and fused in a crucible, whereby metallic silver is 
formed, which, when the heat is sufficiently increased, will be 
found as a button upon the bottom of the crucible; or if it is 
not desirable to heat to the melting-point of silver, the fritted 
mass is dissolved in hot water, and the solution containing the 
soda and cyanide quickly filtered off from the metallic silver. 
The evaporation of large quantities of fluid, to be sure, is in- 
convenient, and requires considerable time. But the reducing 
process above described is without doubt the most simple and 
least injurious. 

According to the wet method, the bath is strongly acidulated 

with hydrochloric acid, provision being made for the effectual 

carrying off of the hydrocyanic acid liberated. Remove the 

precipitated chloride of silver and cyanide of copper by filtra- 

22 



338 ELECTRO-DEPOSITION OF METALS. 

tion, and, after thorough washing, transfer it to a porcelain dish 
and treat it, with the aid of heat, with hot hydrochloric acid, 
which will dissolve the cyanide of copper. The resulting 
chloride of silver is then reduced to the metallic state by mix- 
ing it with four times its weight of crystallized carbonate of 
soda, and half its weight of pulverized charcoal. The whole is 
made into a homogeneous paste, which is thoroughly dried, 
then introduced into a strongly heated crucible. When all the 
material has been introduced, the heat is raised to promote 
complete fusion, and to facilitate the collection of the separate 
globules of silver into a single button at the bottom of the cru- 
cible, where it will be found after cooling. If granulated silver 
is wanted, pour the metal in a thin stream, and from a certain 
height into a large volume of water. 

A very simple method is as follows: Bring the silver bath 
into flasks, mix the contents of the flasks with zinc dust (zinc 
in a finely divided state) in the proportion of about J^ oz. per 
quart of bath, and shake thoroughly 5 or 6 times every day. 
In five days all the silver is precipitated. Decant the clear 
liquid from the precipitate, wash the latter several times with 
water, and dissolve the zinc contained in the precipitate in pure 
hydrochloric acid. The silver remains behind in pulverulent 
form, and may be dissolved in nitric acid, worked up into sil- 
ver chloride or silver cyanide. In place of zinc, aluminium 
powder may be used for precipitation, the excess of aluminium 
being then dissolved by caustic potash, or caustic soda, solution. 

From acid mixtures used for stripping, the silver may be ob- 
tained as follows: Dilute the acid mixture with 10 to 20 times 
the quantity of water, and precipitate the silver as chloride of 
silver by means of hydrochloric acid. Interrupt the addition 
of hydrochloric acid, when a drop of it produces no more pre- 
cipitate of chloride of silver in the clear fluid. The precipi- 
tated chloride of silver is filtered off, washed, and either directly 
dissolved in potassium cyanide, or the silver is regained as 
metal by fusing the chloride of silver with calcined soda and 
wood charcoal powder, previously thoroughly mixed. 



DEPOSITION OF SILVER. 339 

Still simpler is the reduction of the chloride of silver by pure 
zinc. For this purpose suspend the chloride of silver in water, 
add hydrochloric acid, and place pure zinc rods or granulated 
zinc in the fluid. The zinc dissolving, metallic silver is sepa- 
rated, which is filtered off, washed and dried. 



CHAPTER X. 

DEPOSITION OF GOLD. 

Gold is chiefly found in the metallic state, and generally 
alloyed with more or less silver, copper and iron. The follow- 
ing analyses will serve to show the general composition of the 
native metal : — 

Australia. California. Russia. Wales. 

Gold 94-64 89.10 98.96 89.83 

Silver 4.95 10.50 0.16 9.24 

Copper .... 0.05 .... 

Iron 0.41 0.20 0.35 .... 

100.00 99.80 99-52 99-07 

Gold is one of the few metals possessing a yellow color. 
Precipitated from its solution with green vitriol or oxalic acid, 
it appears as a brown powder without lustre, which on pressing 
with the burnisher acquires the color and lustre of fused gold. 
Pure gold is nearly as soft as lead, but possesses considerable 
tenacity. In order to increase its hardness when used for arti- 
cles of jewelry and for coinage it is mixed with silver or copper. 
The " fineness of gold," or its proportion in the alloy, is usually 
expressed by stating the number of carats present in 24 carats 
of the mixture. Pure gold is stated to be 24 carats "fine;" 
standard gold is 22 carats "fine;" 18 carat gold is a mixture of 
18 parts of gold and 6 of alloy. Gold is the most malleable and 
ductile of the metals ; it may be beaten out into leaves not ex- 
ceeding y^TTffth of a millimeter in thickness. When beaten 
out into thin leaves and viewed by transmitted light gold ap- 
pears green ; when very finely divided it is dark red or black. 
The specific gravity of fused gold is 19.35, and of precipitated 
gold powder from 19.8 to 20.2. Pure gold melts at about 
201 6° F., and in fusing exhibits a sea-green color. The melt- 

(34o) 



DEPOSITION OF GOLD. 34 1 

ing-points of alloyed gold vary according to the degree of fine- 
ness. Thus, 23 carat gold melts at 2012 F. ; 22 carat at 
2009 
1992 
1982 



O. jQ - n ^f 4- T/^o,rO 



20 carat at 2002"; 18 carat at 1995 , 15 carat at 
13 carat at 1990 ; 12 carat at 1987 ; 10 carat at 
9 carat at 1979 ; 8 carat at 1973 ; 7 carat at i960 . 
The fineness of gold may be approximately estimated by means 
of the touch-stone, a basaltic stone formerly obtained from Asia 
Minor, but now procured from Saxony and Bohemia. The 
sample of gold to be tested is drawn across the stone, and the 
streak of metal is treated with dilute nitric acid. From the 
rapidity of the action and the intensity of the green color pro- 
duced — due to the solution of the copper — as compared with 
streaks made by alloys of known composition, the assayer is 
enabled to judge of the proportion of inferior metal which is 
present. Gold preserves its lustre in the air and is not acted 
upon by any of the ordinary acids. Nitric, hydrochloric, or 
sulphuric acid by itself does not dissolve gold, but it dissolves 
in acid mixtures which develop chlorine, hence in aqua regia 
(nitro-hydrochloric acid). 

The gold found in commerce under the name of shell-gold or 
painter s gold, which is used in painting and for repairing 
smaller defects in electro gilding, is prepared by triturating 
waste in the manufacture of leaf gold with water, diluted honey 
or gum- water. Gold solution may also be precipitated with 
antimonic chloride. The resulting precipitate is triturated with 
barium hydrate, extracted with hydrochloric acid, and after 
washing, the gold powder is triturated with gum arabic solution. 

Gold baths. Gold-plating may be effected in a hot or cold 
bath, large objects being generally plated in the latter, and 
smaller objects in the former. The hot bath has the advantage 
of requiring less current-strength, besides yielding deposits of 
greater density and uniformity and of sadder, richer tones. 
Hot baths work with a moderate content of gold — nj^ to 
12^ grains per quart of bath — while cold baths should con- 
tain not less than 54 grains per quart. 

Some authors — for instance, Eisner, Briant, Selm, and others 



342 ELECTRO-DEPOSITION OF METALS. 

— give the preference to baths prepared with potassium ferro- 
cyanide; while others, like Elkington and Regnault, work with 
a solution of gold-salt and potassium bicarbonate ; and Bottger, 
Leuchtenberg, and others recommend a solution of cyanide of 
gold in potassium cyanide. With proper treatment of the bath, 
good results may be obtained with either. However, the use 
of baths prepared with potassium ferrocyanide cannot be recom- 
mended on account of the secondary decompositions which 
take place during the operation of plating, and because the 
baths do not dissolve the gold anodes. In the following, only 
approved formulae for the preparation of gold baths will be 
given : — 

I. Bath for cold gilding. — Fine gold in the form of fulmi- 
ating gold 54 grains, 98 per cent, potassium cyanide 0.35 to 
0.5 oz. (according to the current-strength used), water 1 quart. 

To prepare this bath, dissolve 54 grains of fine gold in aqua 
regia in a porcelain dish heated over a gas or alcohol flame, and 
evaporate the solution to dryness. Continue the heating until 
the solution is thickly fluid and dark brown, and on cooling 
congeals to a dark brown, foliated mass. Heating too strongly 
should be avoided, as this would cause decomposition and the 
auric chloride would be converted into aurous chloride, and 
eventually into metallic gold and escaping chlorine. The 
neutral chloride of gold prepared in this manner is dissolved in 
1 pint of water and aqua ammonia added to the solution as 
long as a yellow-brown precipitate is formed, avoiding, how- 
ever, a considerable excess of aqua ammonia. The precipitate 
of fulminating gold is filtered off, washed, and dissolved in 1 
quart of water containing 0.5 oz. of potassium cyanide in solu- 
tion. The solution is boiled, replacing the water lost by evap- 
oration, until the odor of ammonia which is liberated by dissolv- 
ing the fulminating gold in potassium cyanide disappears, when 
it is filtered. Instead of dissolving the gold and preparing 
neutral chloride of gold by evaporating, it is more convenient 
to use 108 grains of chemically pure neutral chloride of gold 
as furnished by chemical works, and precipitate the fulminat- 
ing gold from its solution. 



DEPOSITION OF GOLD. 343 

Too large an excess of potassium cyanide yields gold depos- 
its of an ugly, pale color. When working with a more power- 
ful current, the excess of potassium cyanide need only be slight ; 
with a weaker current it must be larger. With 10 per cent, 
excess of free potassium cyanide, the most suitable current- 
strength is 3 volts. 

The fulminating gold should not be dried, as in this condi- 
tion it is highly explosive, but should be immediately dissolved 
while in a moist state. 

For cold gilding, Roseleur recommends the follo.wing bath: 

II. Fine gold as neutral chloride of gold, 0.35 oz. ; 98 per 
cent, potassium cyanide, 0.7 oz. ; water, 1 quart. 

Dissolve the gold-salt from 0.35 oz. of fine gold or about 0.7 
oz. of neutral chloride of gold in y 2 pint of the water, and the 
potassium cyanide in the other y 2 pint of water, and after 
mixing the solutions boil for half an hour. The preparation of 
this bath is more simple than that of formula I., but the color 
of the gold deposit obtained with the latter is warmer and sad- 
der. The high content of gold in the bath, prepared according 
to formula II., readily causes a red-brown gold deposit, and 
hence special attention has to be paid to the regulation of the 
current. 

For those who prefer gold baths prepared with yellow prus- 
siate of potash instead of potassium cyanide, the following 
formula for cold gilding is given: 

III. Yellow prussiate of potash (potassium ferrocyanide), 
0.5 oz. ; carbonate of soda, 0.5 oz. ; fine gold (as chloride of 
gold or fulminating gold), 30.75 grains; water, 1 quart. 

To prepare the bath, heat the solutions of the yellow prussi- 
ate of potash and of the carbonate of soda in the water to the 
boiling point, add the gold-salt, and boil y hour, or with use 
of freshly precipitated fulminating gold, until the odor of am- 
monia disappears. After cooling, the solution is mixed with a 
quantity of distilled water, corresponding to the water lost by 
evaporation, and filtered. This bath gives a beautiful bright 
gilding upon all metals, even upon iron and steel. 



344 ELECTRO-DEPOSITION 0F METALS. 

This bath is especially suitable for the so-called French gild- 
ing. The articles are first provided with a heavy deposit of 
copper in the alkaline copper bath, then matt coppered in 
the acid copper bath, next drawn through the bright-pickl- 
ing bath, thoroughly rinsed, and finally gilded in the bath 
heated to about 122 F. Suitable current-strength for the cold 
bath 3.0 to 3.25 volts; for the warm bath, 1.5 to 2 volts. 

Gold bath for hot gilding. — IV. Fine gold (as fulminating 
gold) 15.4 grains, 98 per cent, potassium cyanide JJ grains, 
water I quart. 

This bath is prepared in the same manner as that according 
to formula I., from 15.4 grains of fine gold, which is converted 
into neutral chloride of gold by dissolving in aqua regia and 
evaporating ; or dissolve directly 29.32 to 30.75 grains of 
chemically pure neutral chloride of gold in water, precipitate 
the gold as fulminating gold with aqua ammonia, wash the pre 
cipitate, dissolve it in water containing the potassium cyanide, 
and heat until the odor of ammonia disappears, replacing the 
water lost by evaporation. This bath yields a beautiful sad 
gilding of great warmth. All that has been said in regard to 
the content of potassium cyanide in the bath prepared accord- 
ing to formula I. also applies to this bath. The temperature 
should be between 15 8° and 176 F., and the current-strength 
2.0 to 2.5 volts. 

Roseleur recommends for hot electro-gilding: 

V. Chemically pure crystallized sodium phosphate 2.1 1 ozs., 
neutral sodium sulphide 0.35 oz., potassium cyanide 30.86 
grains, fine gold (as chloride) 15.43 grains, distilled water I 
quart. 

If this bath is to serve for directly plating steel, only 15.43 
instead of 30.86 grains of potassium cyanide are to be used. 
Dissolve in a porcelain dish, with the aid of moderate heat, the 
sodium phosphate and sodium sulphide, and when the solution 
is cold, add the neutral chloride of gold prepared from 15.43 
grains of gold = about 30.86 grains of commercial chloride of 
gold, and the potassium cyanide. For use, heat the bath to 
between 15 8° and 167 F. 



DEPOSITION OF GOLD. 345 

Conrad Taucher recommends the following formulae for hot 
gilding: — 

VI. ' Sodium phosphate 14 ozs., sodium bisulphite 3^ ozs., 
sodium bicarbonate 1 ^ ozs., caustic potash t fy ozs -> potas- 
sium cyanide 14 drachms, gold in the form of neutral chloride 
&*4 drachms, distilled water 10 quarts. 

With the exception of the chloride of gold, all the salts may 
be dissolved together. The solution, if necessary, is filtered 
and the gold solution added. The bath is used at between 122 
and 140 F. It yields a very beautiful gilding, but requires 
quite a strong current for its decomposition. It is not suitable 
for the direct gilding of steel. 

VII. Yellow prussiate of potash (potassium ferrocyanide) 5^ 
ozs., pure potassium carbonate 1^ ozs., sal ammoniac iij£ 
drachms, gold in the form of neutral chloride $*4 drachms, 
water 5 quarts. 

Dissolve with the assistance of heat the first three salts, filter, 
and when cold add the chloride of gold. Then heat again and 
boil for half an hour, replacing the water lost by evaporation. 

Many electro-platers prepare the gold baths with the assist- 
ance of the electric current. For this purpose prepare a solu- 
tion of 3.52 ozs. of potassium cyanide (98 to 99 per cent.) per 
quart of water, and after heating to between 122 and 140 F., 
conduct the current of two Bunsen elements through two sheets 
of gold, not too small, which are suspended as electrodes in the 
potassium cyanide solution. The action of the current is inter- 
rupted when the solution is so far saturated with gold that an 
article immersed in it and connected to the negative pole in 
place of the other gold sheet, is gilded with a beautiful warm 
tone. By weighing the sheet of gold serving as anode, the 
amount of gold which has passed into the solution is ascer- 
tained. According to English authorities, a good gold bath 
prepared according to this method should contain 3.52 ozs. of 
potassium cyanide and 0.7 oz. of fine gold per quart of water. 

The only advantage of this mode of preparing the bath is that 
it excludes a possible loss of gold, which may occur in dissolv- 



34^ ELECTRO-DEPOSITION OF METALS. 

ing gold, evaporating the gold solution, etc., by breaking the 
vessel containing the solution. However, by using commercial 
chemically pure chloride of gold such loss is avoided, and the 
bath prepared according to the formulae given yields richer 
tones than a gold bath produced by electrolysis. Besides, the 
preparation of the gold bath with the assistance of the electric 
current can only be considered for smaller baths, since the sat- 
uration of a larger volume of potassium cyanide solution re- 
quires considerable time, and the potassium cyanide is strongly 
decomposed by long heating. 

Management of gold baths. — It is advisable to keep the con- 
tent of gold in the baths prepared according to the different 
formulae as constant as possible, which is best effected by the 
use of fine gold anodes. Insoluble platinum anodes are better 
liked in gilding than for all other electro-plating processes, 
partly because they are cheaper, and partly because they are 
recommended in most books on the subject. However, a bath 
which has become low in gold does not yield a beautiful gold 
color, and has to be frequently strengthened by the addition of 
chloride of gold, the preparation of which consumes time and 
causes expense, so that the use of gold anodes is the cheapest 
in the end. 

The use of steel anodes for cold and warm cyanide gold 
baths, advocated by some, cannot be recommended. Every 
gilder knows from experience that, when the enamel of the vats 
containing the gold baths becomes defective, the baths in a 
short time fail. The reason for this is simply that the iron on 
the defective places of the vat decomposes the gold bath, me- 
tallic gold being separated. Iron, in this respect, acts like 
zinc, which, in a still shorter time, precipitates metallic gold 
from gold baths. Now, when iron anodes remain suspended 
in the baths, a separation of gold takes place, while a quantity 
of iron equivalent to the separated gold is dissolved, and, in 
the form of ferric oxide, falls to the bottom of the vat. 

In hot gold baths this separation of gold proceeds still more 
rapidly and the content of potassium cyanide in the bath is 



DEPOSITION OF GOLD. 347 

destroyed, yellow prussiate of potash being formed. The 
argument made in favor of the use of steel anodes, that the old 
practitioners often added intentionally yellow prussiate of 
potash to their baths to heighten the gold tone, is fallacious. 
A plater who works with gold baths prepared with yellow 
prussiate of potash cannot expect to replace the gold by the 
solution of the gold anodes, and when working with gold 
cyanide and potassium cyanide baths there is no inducement 
for gradually changing the bath into a yellow prussiate of 
potash bath by the use of steel anodes. 

According to one statement, a hot gold bath with steel anodes 
showed, after being electrolyzed for 70 hours, scarcely a trace 
of iron. To ascertain the correctness of this statement by an 
experiment, a gold bath prepared according to formula IV., 
was electrolyzed at 158 F., with a blue annealed steel anode 
weighing 12.092 grammes. During the first two hours only a 
moderate yellow-reddish bloom of iron salt was perceptible on 
the anode, which became detached from the latter and fell to 
the bottom of the beaker. The bloom, however, became 
gradually heavier, the bottom of the beaker was covered with 
a precipitate of a yellow brown color, the previously colorless 
bath acquired a yellow color, and after electrolyzing for five 
hours, the blue color of the anode had largely disappeared. 
The anode weighed now 11.822 grammes, and had conse- 
quently lost 2.2 per cent. After again suspending it in the 
bath it was more rapidly attacked in consequence of the de- 
struction of the blue annealing color which retarded corrosion. 
After five more hours the anode weighed 11.105 grammes, the 
loss being therefore 8.16 per cent. The bath now showed a 
deep yellow color, and the precipitate on the bottom of the 
beaker had increased, while small, lighter flakes of ferric 
hydrate spun around in the bath and attached themselves to 
the anode. Electrolysis was now discontinued, since the last 
mentioned phenomena proved the uselessness of steel anodes 
for the reasons given under " Deposition of Nickel and Cobalt." 

As regards the advantage claimed for the use of steel anodes 



34 8 ELECTRO-DEPOSITION OF METALS. 

that a large anode surface corresponding to the object surface 
can be rendered effective without taxing too severely the 
pocket-book of the gilder, it may be said that the same object 
can in a more rational manner be attained by employing carbon 
anodes which, to prevent contamination of the bath by parti- 
cles of carbon, are placed in linen bags. Crosses and balls of 
unusually large dimensions for church towers have frequently 
been gilded in Dr. Geo. Langbein & Co.'s establishment, for 
which a large anode surface was required in order to obtain a 
uniformly heavy deposit, and in such cases carbon anodes of 
the best quality of retort graphite were used. These anodes, 
to be sure, become saturated with gold bath, and for that rea- 
son cannot be used for other baths. When not required for 
some time, they are kept in a vessel filled with clean water, and 
the latter is added to the bath to replace that lost by evapo- 
ration. 

The employment of anodes of platinum strips or platinum 
wire may, perhaps, be advocated for coloring the deposit, i. e. y 
for the purpose of obtaining certain tones of color when gilding 
in the hot bath. By allowing the platinum anode to dip only 
slightly in the bath a pale gilding is obtained, because the cur- 
rent thereby becomes weaker ; by immersing the anode deeper 
the color becomes more yellow, and by immersing it entirely 
the tone becomes more reddish. However, instead of produc- 
ing these effects of the current-strength by the anode, which 
requires the constant presence of the operator, it is better to 
obtain the coloration by means of the resistance board. By 
placing the switch upon " strong " a reddish gold tone is ob- 
tained, and by placing it upon " weak" a paler gold tone, while 
the beautiful gold yellow lies in the middle between the two ex- 
tremes. However, since even with the use of gold anodes the 
content of gold in the bath is not entirely restored, the bath has 
after some time to be strengthened, which is effected by a solu- 
tion of fulminating gold or chloride of gold in potassium 
cyanide, according to the composition of the bath. 

The excess of potassium cyanide must not be too large, 



DEPOSITION OF GOLD. 



349 



otherwise the gilding will be pale ; but, on the other hand, it 
must not be too small, since in this case quite a strong current 
would have to be used to effect a normal deposition of gold, 
which, besides, would not be dense and homogeneous. 

As in the silvering baths, the excess of potassium cyanide in 
the gold baths is also partially converted into potassium carbo- 
nate by the action of the air, the heat, etc., and it is, therefore, 
advisable from time to time to add a small quantity of potas- 
sium cyanide. 

Gold baths for cold gilding are kept in vats of stoneware or 
enameled iron, or small baths in glass vats, which, to protect 



Fig. 135, 




them against breaking, are placed in a wooden box. Baths for 
hot gilding require enameled iron vats in which they can be 
heated by a direct fire, or better, by placing in hot water (water 
bath), or by steam. For small gold baths for hot gilding, a 
porcelain dish resting upon a short-legged iron tripod may be 
used, (Fig. t 35 . ) Beneath the iron tripod is a gas burner 
supplied with gas by means of a flexible India-rubber tube 
connected to an ordinary gas burner. Across the porcelain 
dish are placed two glass rods, around which the pole-wires are 
wrapped. In heating larger baths in enameled vats over a 



350 ELECTRO-DEPOSITION OF METALS. 

direct fire it may happen that on the places most exposed to 
the heat the enamel may blister and peel off; it is, therefore, 
better to heat the baths in a water or steam bath. For this 
purpose have made a box of stout iron or zinc sheet about 
Y^ inch wider and longer, and about 4 inches deeper than the 
enameled vat containing the gold bath. To keep the level of 
the water constant, the box is to be provided with a water 
inlet and overflow pipe. In this box place the vat so that its 
edges rest upon those of the box, and make the joints tight 
with tow. The water-bath is then heated over a gas flame or 
upon a hearth, the water lost by evaporation being constantly 
replaced, so that the enameled vat is always to half its height 
surrounded by hot water. For heating by steam the arrange- 
ment is the same, only a valve for the introduction, and a pipe 
for the discharge, of steam, are substituted for the water inlet 
and overflow pipe. 

Execution of gold 'plating — r-Most suitable current density, 
O.15 to 0.2 ampere. Like all other electro-plating operations, 
it is advisable to effect gold-plating with an external source of 
current, that is, to use a battery or other source of current sepa- 
rated from the bath, and to couple the apparatuses as previously 
described and illustrated by Figs. 54 and 55. 

To be sure, there are still gilders who gild without a battery 
or separate external source of current and obtain good results, 
the process being, as a rule, employed only in gilding small 
articles. The apparatus used for this purpose consists of a glass 
vessel containing the gold solution compounded with a large 
excess of potassium cyanide and a porous clay cell filled with 
very dilute sulphuric acid or common salt solution, which is 
placed in the glass vessel. Care should be taken to have the 
fluids in both vessels at the same level. Immerse in the clay 
cell an amalgamated zinc cylinder or zinc plate, to which a 
copper wire is soldered. Outside the cell this copper wire is 
bent downwards, and the article to be gilded, which dips in the 
gold solution, is fastened to it. In working with this apparatus 
there is always a loss of gold, since the gold solution penetrates 



DEPOSITION OF GOLD. 351 

through the porous cell, and on coming in contact with the zinc 
is reduced by it, the gold being separated as black powder upon 
the zinc. In cleaning the apparatus this black slime has to be 
carefully collected and worked for fine gold. 

For the sake of greater solidity, only articles of silver and 
copper and its alloys should be directly gilded, while all other 
metals are best first brassed or coppered. Cleaning from 
grease and pickliug is done in the same manner, as described 
on page 169. The preparation of the articles for gilding differs 
from that for silvering only in that the surfaces which later on 
are to appear with high lustre are not artificially roughened 
with emery, pumice, or by pickling, because, on the one hand, 
the gold deposit seldom needs to be made extravagantly heavy, 
and the rough surface formed would require more laborious 
polishing, with the burnishers; and, on the other, the gold de- 
posits adhere quite well to highly-polished surfaces, provided 
the current strength is correctly regulated, and the bath 
accurately composed according to one of the formulae given. 
Quicking the articles before gilding, which is recommended by 
some authors, is not necessary. 

The current-strength must, under no circumstances, be so 
great that a decomposition of water and consequent evolution 
of hydrogen on the objects takes place, since otherwise the gold 
would not deposit in a reguline and coherent form, but as a 
brown powder. By regulating the current- strength so that it 
just suffices for the decomposition of the bath, and avoiding a 
considerable surplus, a very dense and uniform deposit is 
formed; and by allowing the object to remain long enough in 
the bath, a beautiful, matt gold deposit can be obtained in all 
the baths prepared according to the formulae given. It may, 
however, be mentioned that this mode of matt gilding is the 
most expensive, since it requires a very heavy deposit, and it 
will, therefore, be better to matten the surface previous to gild- 
ing, according to a process to be described later on. ;•••■ 

For gilding with cold baths two freshly filled Bunsen ele- 
ments coupled for tension suffice in almost all cases;' while 



352 ELECTRO-DEPOSITION OF METALS. 

for hot baths one element is, as a rule, sufficient, if the anode 
surface is not too small. The more electro-positive the metal 
to be gilded is, the weaker the current can and must be. 

Though gold solutions are good conductors and, therefore, 
the portions of the articles which do not hang directly opposite 
the anodes gild well, for the solid plating of larger objects it is 
recommended to frequently change their positions except 
when they are entirely surrounded by anodes. 

The inner surfaces of hollow -ware, such as drinking-cups, 
milk pitchers, etc., are best plated after freeing them from 
grease and pickling, by filling the vessel with the gold bath and 
suspending a current-carrying gold anode in the centre of the 
vessel, while the outer surface of the latter is brought in con- 
tact with the negative conducting wire. The lips of vessels are 
plated by placing upon them a cloth rag saturated with the 
gold bath and covering the rag with the gold anode. 

For gold-plating in the cold bath the process is as follows : 
The objects, thoroughly freed from grease and pickled (and if 
of iron, zinc, tin, Britannia, etc., previously coppered), are 
suspended in the bath by copper wires, where they remain 
with a weak current until in about 8 or 10 minutes they appear 
uniformly plated. At this stage they are taken from the bath, 
rinsed in a pot filled with water, the latter, after having been 
used for some time, is added to the bath to replace the water 
lost by evaporation. The articles are finally brushed with a fine 
brass scratch-brush and tartar solution, thoroughly rinsed, again 
freed from grease by brushing with lime-paste and then re- 
turned to the bath, where they remain until they have acquired 
a deposit of sufficient thickness. 

If it is intended to give them a very heavy deposit, it is ad- 
visable to scratch-brush them several times with the use of 
tartar or its solution. For gold-plating by weight the same 
plan as given for silver-plating (p. 311) is pursued. 

For gold-plating with the hot bath the operations are the same, 
with the exception that a weaker current is introduced into the 
bath and the time of the plating process shortened. Frequent 



DEPOSITION OF GOLD. 353 

scratch-brushing also increases the solidity of the deposit and 
prevents its prematurely turning to a dead brown-black. Since 
in hot plating more gold than intended is readily deposited, it 
is especially advisable to place a resistance board in the circuit, 
as otherwise the operator must remain standing alongside of the 
bath and regulate the effect of the current by immersing the 
anodes more or less. 

With a somewhat considerable excess of potassium cyanide, 
and if the objects to be plated are not rapidly brought in con- 
tact with the current-carrying object rod, hot gold baths cause 
the solution of some metal. Therefore, when silver or silver- 
plated objects are constantly plated in them they yield a some- 
what greenish gilding in consequence of the absorption of silver, 
or a reddish gilding due to the absorption of copper, if copper 
or coppered articles are constantly plated in them. Hence, for 
the production of such green or reddish color, gold-plating 
baths which have thus become argentiferous or cupriferous 
may be advantageously used. In order to obtain a deposit of 
green or red gold with fresh baths, the tone-giving addition 
of metal must be artificially effected, as will immediately be 
seen. 

If, however, such extreme tones are not desired, the content 
of gold in the baths may be exhausted for preliminary plating 
with the use of platinum anodes, the sad gold color being then 
given in a freshly prepared bath. 

The gold deposits are polished, in the same manner as silver 
deposits, with the burnisher and red ochre, and moistening 
with solution of soap, decoction of flaxseed, or soap-root, etc. 

Red gilding. — In order to obtain a red gold with the formulae 
given, a certain addition of copper cyanide dissolved in potas- 
sium cyanide has to be made to them. The quantity of such 
addition cannot be well expressed by figures, since the current- 
strength with which the articles are plated exerts considerable 
influence. It is best to triturate the copper cyanide in a mor- 
tar to a paste with water, and add of this paste to a moderately 
concentrated potassium cyanide solution as long as copper 
23 



354 ELECTRO-DEPOSITION OF METALS. 

cyanide is dissolved. Of this copper solution add, gradually 
and in. not too large portions, to the gold solution until, with 
the current-strength used, the gold deposit shows the desired 
red tone. The absorption of copper by the bath may also be 
effected by replacing the gold anodes by copper anodes and cir- 
culating the current (suspending a few gold anodes to the object 
rod). The direct addition of copper cyanide is, however, 
preferable. 

For the determination of the content of copper required for 
the purpose of obtaining a beautiful red gold, a bath for hot 
gilding which contained 10.8 grains of gold per quart was com- 
pounded with a solution of copper cyanide in potassium cyanide 
with 1.08 grains content of copper. The tone of the gilding, 
which previously was pure yellow, immediately passed into a 
pale red gold. By the further addition of 1.08 grains of cop- 
per a fiery red gold tone was obtained, while a third addition of 
1.08 grains of copper yielded a color more approaching that of 
copper than of gold. These experiments show that 20 per 
cent, of copper of the weight of gold contained in the bath 
seems to be the most suitable proportion for obtaining a beau- 
tiful red gold. 

Green gilding. — To obtain greenish gilding, solution of 
cyanide or chloride of silver in potassium cyanide has to be 
added to the gold bath. It is not easy to prepare greenish 
gilding of a pleasing color, and to obtain it the current-strength 
must be accurately proportioned to the object surface, since with 
too weak a current silver predominates in the deposit, the gild- 
ing then turning out whitish, whiletoo strong a current deposits 
too much gold in proportion" to silver, the gilding becoming 
yellow, but not green. 

Rose-color gilding may be obtained by the addition of suit- 
able quantities of copper and silver solutions, but such coloration 
reqires much attention and thought. 

Matt gilding. — As previously mentioned, a beautiful matt 
gold deposit may be obtained by the use of any of the for- 
mulas given, and a current correctly regulated, and allowing 



DEPOSITION OF GOLD. 3«5 5 

sufficient time for gilding. The heavy deposit of gold required 
for this process makes it, however, too expensive, and it is, 
therefore, advisable to produce matt gilding by previously 
matting the basis-surface, since then a thinner deposit of gold 
will answer very well. The process of graining has already 
been described on p. 326. Another method is to matt the first 
deposit with the scratch-brush, and then to give a second de- 
posit of gold which also turns out matt upon the matted sur- 
face. However, the operation of matting with the scratch- 
brush requires considerable skill. 

Articles may be readily matted with the use of the sand blast, 
after which they are quickly drawn through the bright-dipping 
bath, thoroughly rinsed, and brought into the gold bath. 

In the chemical or electro-chemical way, matting is effected 
by one of the following methods: 

For this purpose the mixture of 1 volume of saturated solu- 
tion of bichromate of potash and 2 volumes of concentrated 
hydrochloric acid, mentioned on p. 165, may be used. Brass 
articles are allowed to remain several hours in the mixture, 
and are then quickly drawn through the bright-dipping bath. 
Copper alloys may also be successfully matted by suspending 
them as anodes in a mixture of 90 parts water and 10 parts 
sulphuric acid, and drawing the matted articles through the 
bright-dipping bath. 

Or, they are matt silvered and the gold is deposited upon the 
matted layer of silver. Articles gilded upon a matt silver 
basis, however, acquire before long an ugly appearance, since 
in an atmosphere containing sulphuretted hydrogen, the silver 
becomes black, even under the layer of gold, and shines 
through. 

More advantageous is the process of providing the articles 
with a matt copper coating in the acid galvanoplastic bath. 
They are then drawn through a not too strong pickle, rinsed, 
and gilded. This process is used for the so-called French 
gilding, and yields a very sad, beautiful gilding. The articles 
consisting of zinc are first heavily coppered in a cyanide cop- 



356 ELECTRO-DEPOSITION OF METALS. 

per bath, then matted in the acid copper bath (see " Galvano- 
plasty "), care being taken that the slinging wire is in contact 
with the object-rod, which conducts the current, before the 
coppered zinc object is suspended in the bath. This process 
of coppering of zinc in the acid copper bath is, however, quite 
a delicate operation, and it will frequently be noticed, even 
with apparently very heavy coppering in the cyanide copper 
bath, that in suspending the articles in the acid bath, brownish- 
black places appear on which, by contact of the acid bath with 
zinc, copper in a pulverulent form is deposited. When this is 
observed, the articles must be immediately taken from the bath, 
thoroughly scratch-brushed, and again thoroughly and heavily 
coppered in the cyanide copper bath, before replacing them in 
the acid copper bath. It may be recommended to provide 
the coppered zinc articles with a thick deposit of nickel, and 
then to copper them matt in the acid bath, the percentage of 
unsuccessful coppering being much smaller than without pre- 
vious nickeling. The matt-coppered articles are rapidly drawn 
through the bright-dipping bath and then gilded, the bath pre- 
pared according to formula III., and heated to about 140 F., 
being very suitable for the purpose. 

Coloring of the gilding. — It has been frequently mentioned 
that the most rational and simple process of giving certain 
tones of color to the gilding is by means of a stronger or weaker 
current. Many operators, however, cling to the old method of 
effecting the coloration by gilder's wax or brushing with certain 
mixtures, and for this reason this process, which is generally 
used for coloring fire-gilding, shall be briefly mentioned. 

To impart to the gold-deposit a redder color, the gilding-wax 
is prepared with a greater content of copper, while for greenish 
gilding more zinc-salt is added. There are innumerable re- 
ceipts for the preparation of gilding-wax, nearly every gilder 
having his own receipt, which he considers superior to all 
others. Only two formulae which yield good results will here 
be given, one (I.) for reddish gilding and one (II.) for green- 
ish gilding. 



DEPOSITION OF GOLD. 357 

I. Wax 12 parts by weight, pulverized verdigris 8, pulver- 
ized sulphate of zinc 4, copper scales 4, borax 1, pulverized 
bloodstone 6, copperas 2. 

II. Wax 12 parts by weight, pulverized verdigris 4, pulver- 
ized sulphate of zinc 8, copper scales 2, borax 1, pulverized 
bloodstone 6, copperas 2. 

Gilder's wax is prepared as follows : Melt the wax in an iron 
kettle, add to the melted mass, whilst constantly stirring, the 
other ingredients, pulverized and intimately mixed, in small 
portions, and stir until cold, so that the powder cannot settle 
on the bottom or form lumps. Finally, mould the soft mass 
into sticks about % inch in diameter. 

Gilder's wax is applied as follows : Coat the heated gilded 
articles uniformly with the wax and burn off over a charcoal 
fire, frequently turning the articles. After the wax flame is 
extinguished, plunge the articles into water, scratch-brush with 
wine-vinegar, dry in sawdust, and polish. 

To give gilded articles a beautiful, rich appearance, the fol- 
lowing process may also be used : Mix 3 parts by weight of 
pulverized alum, 6 of saltpetre, 3 of sulphate of zinc, and 3 of 
common salt, with sufficient water to form a thinly-fluid paste. 
Apply this paste as uniformly as possible to the articles by 
means of a brush, and after drying, heat the coating upon an 
iron plate until it turns black ; then wash in water, scratch- 
brush with wine-vinegar, dry, and polish. 

According to a French receipt, the same result is attained by 
mixing pulverized blue vitriol 3 parts by weight, verdigris 7, 
sal ammoniac 6, and saltpetre 6, with acetic acid 31 ; immers- 
ing the gilded articles in the mixture or applying the latter 
with a brush ; then heating the objects upon a hot iron plate 
until they turn black, and, after cooling, pickling in concen- 
trated sulphuric acid. 

Some gilders improve bad tones of gilding by immersing the 
articles in dilute solution of nitrate of mercury until the gilding 
appears white. The mercury is then evaporated over a flame 
and the articles are scratch-brushed. Others apply a paste of 



358 



ELECTRO-DEPOSITION OF METALS. 



pulverized borax and water, heat until the borax melts, and 
then quickly immerse in dilute sulphuric acid. 

Incrustations with gold are produced in the same manner as 
incrustations with silver described on p. 329. 

Gilding of metallic wire and gauze. — Fine wire of gilded 
copper and brass is much used in the manufacture of metallic 
fringes and lace, for epaulettes and other purposes. The fine 
copper and brass wires being drawn through the draw-irons 
and wound upon spools by special machines, and hence not 
touched by the hands, freeing from grease may, as a rule, be 

Fig. 136. 




omitted. The first requisite for gilding is a good winding ma- 
chine, which draws the wires through the gold bath and wash 
boxes, and further effects the winding of the wire upon spools. 
The principal demand made in the construction of such a ma- 
chine is that by means of a simple manipulation, a great varia- 
tion in the speed with which the wire or gauze passes through 
the gold bath can be obtained. This is necessary in order to 
be able to regulate the thickness of the gilding by the quicker 
or slower passage of the wire. A machine well adapted for 



DEPOSITION OF GOLD. 359 

this purpose is that constructed by J. W. Spaeth and shown in 
Fig. 136. 

The variation in the passage of the wire is attained by the 
two friction-pulleys F, which sit upon a common shaft with the 
driving-pulley, R, and transmit their velocity by means of the 
friction-pistons KK' to the friction-pulley F'> which is firmly 
connected to the belt-pulley R driving the spool spindle. Since 
by a simple device the pistons K and K' may be shifted, it is 
clear that the transmission of the number of revolutions from 
F to F' is dependent on the position of the friction pistons K 
and K' ', and that the velocity will be the greater the shorter the 
distance they are from the centre of friction- pulleys F and F' . 
In order that the friction between F y K and F' may always be 
sufficient for the transmission of the motion, even when the 
pistons are worn, four weights, G, are provided, which press 
the above-mentioned parts firmly against each other. 

In front of each spool of this machine is inserted a small 
enameled iron vat which contains the gold bath, and is heated 

Ftg. 137. 



by a gas flame to about 167 F. Between this bath and the 
winding machine is another small vat with hot water in which 
the gilded wire is rinsed. 

The wire unwinds from a reel placed in front of the gold 
baths, run over a brass drum which is connected to the nega- 
tive pole of the source of current and transmits the current to 
the wire. The dipping of the wire into the gold bath is 
effected by porcelain drums, which are secured to heavy pieces 
of lead placed across the vats, as shown in Fig. 137. The 
gilded wire being wound upon the spools of the winding 
machine, these spools are removed and thoroughly dried in 



360 ELECTRO-DEPOSITION OF METALS. 

the drying chamber. The wire is then again reeled off on to 
a simple reel, in doing which it is best to pass it through be- 
tween two soft pieces of leather to increase its lustre. 

The most suitable gold bath is that prepared according to 
formula IV. The current-strength should be from 6 to 8 volts, 
which will produce a deposit of sufficient thickness even with 
the wire passing at the most rapid rate through the bath. 

Gilding by contact, by immersion, and by friction. — For contact 
gilding by touching with zinc, formulae I., II., IV. and V., may 
be used, IV. and V. being especially suitable if the addition of 
potassium cyanide is somewhat increased and the baths are 
sufficiently heated. 

A contact gold bath prepared with yellow prussiate of potash 
according to the following formula also yields a good deposit. 

VIII. Fine gold as chloride of gold 54 grains, yellow prussi- 
ate of potash 1 oz., potash r oz., common salt 1 oz., water 
1 quart. The bath is prepared as given for formula III. For 
use, heat it to boiling. 

Gilding by contact is done the same way as silvering by con- 
tact. The points of contact must be frequently changed, since 
in the gold bath intense stains are still more readily formed 
than in the silver bath. 

For gilding by contact, Conrad Taucher recommends the 
following bath : Distilled water 10 quarts, sodium or potassium 
pyrophosphate 28 ozs., prussic acid 4^ drachms, crystallized 
chloride of gold 13^ drachms. 

To prepare the bath, bring into a porcelain vessel or into a 
dish of enameled cast-iron 9 quarts of distilled * water and add 
the 28 ozs. of pyrophosphate, stirring constantly with a glass 
rod. Then heat, and when solution is complete filter and set 
aside to cool. 

While filtering the solution, the chloride of gold is prepared 
by bringing into a small glass flask 5 )/ 2 drachms of fine rolled 
gold, 14 drachms of pure hydrochloric acid, and S}4 drachms 

♦The use of distilled water is necessary, otherwise the lime salts contained in 
ordinary water would decompose a portion of the pyrophosphate. 



DEPOSITION OF GOLD. 36I 

of pure nitric acid. Apply a gentle heat to the bottom of the 
flask. In a few seconds vigorous effervescence accompanied 
by the evolution of orange-red vapors takes place, and the gold 
in a few minutes dissolves to a reddish-yellow fluid. To evapo- 
rate an excess of acids, which if brought into the bath might 
cause serious disturbances and even render the bath entirely 
useless, the flask is placed upon a piece of sheet-iron provided 
in the centre with a hole- about 0.11 inch in diameter, and 
heated upon a stove or over a spirit lamp. When no more 
vapors escape and the solution has become thickly-fluid and 
has acquired an intense hyacinth-red color, remove the flask 
from the fire by means of wooden pincers and let cool. If prop- 
erly prepared, the chloride of gold then congeals to an aggre- 
gate of saffron-yellow acicular crystals. If the color of the 
latter is red, too much heat has been applied. Such chloride 
of gold is very suitable for the preparation of electro-gilding 
baths, but if it is to be used for contact gilding a small quantity 
of the above-mentioned two acids has to be added, and, after 
heating, the mass has to be again evaporated. 

It frequently happens that by careless manipulation the gold 
is " burnt," i. e., the auric chloride is decomposed by too long 
continued heating, and is converted into insoluble aurous 
chloride, or even into pulverulent metallic gold. If such is the 
case, the treatment with the above-mentioned mixture of acids 
has to be repeated. The object of the perforated piece of 
sheet-iron, on which the flask is placed for the purpose of 
evaporating the solution, is to prevent the sides of the flask 
from being heated too strongly, as otherwise the thin layers of 
chloride of gold solution might be decomposed. 

In practice porcelain capsules which are heated in a sand 
bath are generally used for dissolving gold. Fig. 138 shows 
such a capsule with glass funnel in a sand bath over a gas 
stove. The purpose of the glass funnel is to prevent any fluid 
from being thrown from the capsule at the moment of effer- 
vescence caused by the action of the acids upon the metal. 

The cold crystallized chloride of gold in the flask or the cap- 



362 



ELECTRO-DEPOSITION OF METALS. 



sule is now dissolved in a small quantity of distilled water, 
solution being effected almost . immediately. The solution is 
poured upon a filter of filtering paper in a glass funnel placed 
upon a clean bottle. A small piece of paper should be in- 
serted between the funnel and the neck of the bottle, so that 
the air can escape from the latter and the fluid run off from the 
filter. 

The object of filtering is to separate the small quantity of 
chloride of silver formed from the little silver which is present 
even in the purest commercial gold. To bring all the gold 

Fig. 138. 




into the bath, repeatedly wash the bottle and the filter with a 
small quantity of distilled water. 

Now mix the cold solution of the pyrophosphate and that 
of the chloride of gold by pouring the latter gradually into 
the former and stirring with a glass rod. Then add the 4^ 
drachms of prussic acid and heat to the boiling point, when 
the bath is ready for use. 

When mixed cold the bath has a yellow or yellow-greenish 
color, which disappears as the temperature rises. However, 
the fluid sometimes becomes currant-red or violet, which indi- 
cates that it contains too little prussic acid. This is remedied 
by adding drop by drop prussic acid until the fluid is entirely 



DEPOSITION OF GOLD. 363. 

discolored. Great care must, however, be exercised in adding 
the acid, as an excess of it renders the gilding pale. 

By following the directions above given, the bath is very 
suitable for producing a beautiful yellow gilding on objects 
previously thoroughly cleansed. The articles should be passed 
through a very weak solution of mercurous nitrate, otherwise 
the gilding shades and becomes reddish. The articles to be 
gilded must be constantly moved in the bath. They are sus- 
pended to hooks or brought into the bath in dipping baskets 
of stoneware or brass. 

Gilding is finished in a few seconds. The articles are then 
washed in clean water, dried in dry and warm sawdust, and if 
necessary, immediately polished. 

By neglecting the precautionary measures given above, the 
gilding sometimes appears tarnished and dissimilar in tone. It 
is then colored or treated with the so-called matt for gilded 
articles. 

For this purpose melt equal parts of the following salts in 
their water of crystallization at about 21 2° F. : Ferrous sulphate 
(green vitriol), zinc sulphate (white vitriol), alum, and salt- 
petre. 

Thoroughly wet every portion of the defective gilding by 
turning the articles about in this mixture. Then place them in 
the centre of a cylindrical stove, in which the coal burns be- 
tween the sides and a cylindrical grate, so that the entire heat 
radiates toward the empty space in the centre. The salts melt 
and then get into a fiery flux, the entire mass acquiring a dull 
earthen color. When on touching the articles with the moist- 
ened finger a slight hissing noise is heard, the temperature is 
sufficiently high and the articles are thrown into weak starch- 
water acidulated with sulphuric acid. The coating of salt dis- 
solves immediately and the gilding presents a beautiful warm 
and uniform appearance. This operation can, of course, only 
be executed if the entire article has been gilded. 

Baths for gilding by dipping. The following two formulas 
have stood the test: 



364 ELECTRO-DEPOSITION OF METALS. 

I. Crystallized sodium pyrophosphate 2.82 ozs., 12 percent, 
prussic acid 4.51 drachms, crystallized chloride of gold 1. 1 2 
drachms, water 1 quart. Heat the bath to the boiling point, 
and immerse the pickled objects of copper or its alloys, mov- 
ing them constantly until gilded. Iron, steel, tin, and zinc 
should be previously coppered, coating the objects with 
mercury (quicking) being entirely superfluous. 

All gold baths prepared with sodium pyrophosphate, when 
fresh, give rapid and beautiful results, but they have the disad- 
vantage of rapidly decomposing, and consequently can seldom 
be completely exhausted. In this respect the following formula 
answers much better: 

II. Crystalized sodium phosphate 2.82 drachms, chemically 
pure caustic potash 1.69 drachms, chloride of gold 0.56 
drachm, 98 per cent, potassium cyanide 9.03 drachm, water 
1 quart. Dissolve the sodium phosphate and caustic potash in 
^ of the water, and the potassium cyanide and chloride of 
gold in the remaining J^, and mix both solutions. Heat the 
solution to the boiling point. This bath can be almost entirely 
exhausted, it not being decomposed by keeping. Should the 
bath become weak, add about 2^ drachms oi potassium 
cyanide, and use it for preliminary dipping until no more gold 
is reduced. To complete gilding, the objects subjected to such 
preliminary dipping are then immersed for a few seconds in a 
freshly-prepared bath of the composition given above. 

The layer of gold formed is in all cases very thin, the amount 
of gold deposited corresponding to the quantity of basis-metal 
which has been dissolved. 

III. One of the best directions for gilding without the use of 
the current is, according to the " Edelmetallindustrie," as fol- 
lows : Prepare a solution of gold in aqua regia (2 parts hydro- 
chloricacid and 1 part nitric acid). The solution of the gold is 
effected in a porcelain dish, best in a sand or water bath, 
whereby heavy brown acid vapors of hyponitrous acid are 
evolved. When all is dissolved allow the acid to evaporate 
until the fluid has acquired a deep brown color and no more 



DEPOSITION OF GOLD. 365 

acid vapors arise. Then, after cooling, dilute the solution with 
water and keep it in a bottle for future use. Next dissolve in 
the bath 6^ drachms of potassa and 11% drachms of sodium 
phosphate, and add enough gold solution that the bath con- 
tains about 2]/^ drachms of gold. To this bath, containing 
obout 8 to 10 quarts of fluid, add carefully, with constant stir- 
ring, 1 ^ ozs. of potassium cyanide, and then let it thoroughly 
boil for some time. After cooling the bath to about 176 or 
158 F., suspend the articles in it and keep the bath at this tem- 
perature. The bath only requires an occasional addition of gold 
solution (when the gilding becomes gray or dirty), or of potas- 
sium cyanide (when the gilding becomes foxy), and, with 
proper treatment, can be used for a long time. 

Gilding of porcelain, glass, etc. — The pyrophosphate baths 
given above may be advantageously employed for gilding 
porcelain, glass, stoneware, etc., the process being as follows: 

Neutral platinic chloride is intimately triturated with enough 
lavender oil to form a thin syrup. Of this preparation a 
scarcely perceptible film is applied by means of a small brush 
to the article to be ornamented. When dry, the article is 
heated in a muffle to a dark red heat. At this temperature 
the essential oil partially volatilizes, while another portion is 
decomposed, and reduces by its hydrogen the platinic chloride 
to metallic platinum, the result being a coating of metal of a 
finely polished appearance. When cold the article is immedi- 
ately drawn through nitric acid, which does not attack the plat- 
inum, but removes any impurities which might make its surface 
dull. The article is then washed in a large quantity of water, 
wrapped with fine brass wire in such a manner that the wire 
touches the platinized places at many points, and is then 
brought into the gold bath. In a few minutes the platinum is 
coated with a beautiful smooth film of gold, which adheres well, 
and only requires rubbing with chamois. 

By this method the expensive work of polishing is rendered 
unnecessary, which with articles having many depressed places 
is besides almost impossible. If the gilding is too red, add to 



$66 ELECTRO-DEPOSTTION OF METALS. 

the bath a few drops of the double cyanide of potassium and 
silver. 

Gilding by friction . — This process is variously termed gilding 
with the rag, with the thumb, with the cork. It is chiefly em- 
ployed upon silver, though sometimes also upon brass and 
copper. The operation is as follows: Dissolve 1.12 to 1.69 
drachms of chloride of gold in as little water as possible, to 
which has previously been added 0.56 drachm of saltpetre. 
Dip in this solution small linen rags, and, after allowing them 
to drain off, dry them in a dark place. These rags saturated 
with gold solution are then charred to tinder at not too great a 
heat, whereby the chloride of gold is reduced, partially to 
protochloride and partially to finely divided metallic gold. 
This tinder is then rubbed in a porcelain mortar to a fine uni- 
form powder. 

To gild with this powder, dip into it a charred cork moistened 
with vinegar or salt water and rub, with not too gentle a pres- 
sure, the surface of the article to be gilded, which must be 
previously cleansed from adhering grease. The thumb of the 
hand may be used in place of the cork, but in both cases care 
must be had not to moisten it too much, as otherwise the pow- 
der takes badly. After gilding, the surface may be carefully 
burnished. 

For gilding by friction, a solution of chloride of gold in an 
excess of potassium cyanide may also be used, after thickening 
the solution to a paste by rubbing in whiting. The paste is 
applied to the previously zincked metals by means of a cork, a 
piece of leather, or a brush. Martin and Peyraud, the origina- 
tors of this method, describe the operation as follows : Articles 
of other metals than zinc are placed in a bath consisting of con- 
centrated solution of sal ammoniac, in which has been placed 
a quantity of granulated zinc. The articles are allowed to boil 
a few minutes, whereby they acquire a coating of zinc. For 
the preparation of the gilding composition, dissolve 11.28 
drachms of chloride of gold in a like quantity of water, and 
add a solution of 2.1 1 ozs. of potassium cyanide in as little 



DEPOSITION OF GOLD. 367 

water as possible (about 2.8 ozs.). Of this solution add so 
much to a mixture of 3.52 ozs. of fine whiting and 2.82 drachms 
of pulverized tartar that a paste is formed which can be readily 
applied with a brush to the article to be gilded. When the 
article is coated, heat it to between 140 and 1 5 8° F. After 
removing the dry paste by washing, the gilding appears and 
can be polished with the burnisher. 

Fire or mercury gilding. — Before the introduction of electro- 
plating, nearly all substantial gilding was effected by this pro- 
cess. However, the cost is much greater, the execution of the 
process presenting many difficulties, and besides the workman 
is constantly exposed to the very injurious mercurial vapors. 
The resulting gilding, however, is distinguished by great 
solidity. 

The execution of fire gilding begins with the preparation of 
the amalgam of gold. For this purpose put a weighed quantity 
of fine gold in a crucible and heat to dull redness. The requi- 
site proportion of mercury, 8 parts to 1 of gold, is now added, 
and the mixture is stirred with a slightly crooked iron rod, the 
heat being kept up until the gold is entirely dissolved by the 
mercury. Pour the amalgam into a small dish about 3 parts 
filled with water, and work about with the fingers under the 
water to squeeze out as much of the excess of mercury as pos- 
sible. To facilitate this the dish is slightly inclined, to allow 
the superfluous mercury to flow from the mass, which soon 
acquires a pasty condition capable of receiving the impression 
of the fingers. Afterward squeeze the amalgam in a chamois 
leather bag, by which a further quantity of mercury is liberated. 
The amalgam, which remains after this final treatment, consists 
of about 33 parts of mercury and 67 parts of gold in 100 parts. 
The mercury which is pressed through the bag retains a good 
deal of gold, and is employed in preparing fresh batches of 
amalgam. It is important that the mercury employed should 
be pure. 

To apply the amalgam, a solution of nitrate of mercury is 
employed which is prepared by dissolving in a glass flask 100 



368 ELECTRO-DEPOSITION OF METALS. 

parts of mercury in no parts of nitric acid of specific gravity 
1.33, gentle heat being employed to assist the chemical action. 
The red fumes given off must be allowed to escape into the 
chimney, since they are very deleterious when inhaled. When 
the mercury is all dissolved the solution is to be diluted with 
about 25 times its weight of distilled water, and bottled for use. 
The pasty amalgam is spread with the blade of a knife upon 
a hard, flat stone. The article, after being well cleaned and 
scratch-brushed, is treated as follows : Take a small scratch- 
brush, formed of stout brass wire, dip in the solution of nitrate 
of mercury, then draw over the amalgam , pass the brush care- 
fully over the surface to be gilded, repeatedly dipping the 
brush in the mercurial solution and drawing it over the amal- 
gam until the entire surface is uniformly and sufficiently 
coated. Then rinse the article well, and dry. The next 
operation is the evaporation of the mercury. For this purpose 
a charcoal fire, resting upon a cast-iron plate, has been gener- 
ally adopted, a simple hood of sheet-iron being the only means 
of protection from the injurious effects of the mercurial vapors. 
When the amalgamated article is rinsed and dried, it is ex- 
posed to the glowing charcoal, turned about and heated by 
degrees to the proper point, then it is withdrawn from the fire 
by means of long pincers or tongs. The article is then taken 
in the left hand, which should be protected with a leather 
glove, turned over the fire in every direction, and while the 
mercury is volatilizing the article should be struck with a long- 
haired brush to equalize the amalgam coating and force it upon 
such parts as may appear to require it. When the mercury 
has become entirely volatilized the gilding has a dull, greenish- 
yellow color. If any bare places are apparent, they are 
touched up with amalgam and the article is again submitted to 
the fire, care being taken to expel the mercury gradually. The 
article is then well scratch-brushed. When it is of a pale 
greenish color, heat it again to expel any remaining mercury, 
when it acquires the orange -yellow of fine gold. If required 
to be bright, it is burnished in the ordinary way. If the gild- 



DEPOSITION OF GOLD. 369 

ing is to be dead, secure the article by means of iron wire to 
the end of an iron rod and coat it with a hot paste consist- 
ing of saltpetre, common salt, and alum ; then expose the 
article to a bright fire, turning it in every direction until the 
coat of the mixture fuses and begins to run off; then remove 
the article from the fire and throw it in a wooden vat containing 
a large quantity of water. The coat of salts covering the article 
is immediately dissolved, and the gilding presents a beautiful 
dead appearance. To stand this process of deadening, the 
article must be well gilded, especially, as frequently happens, 
if the operation does not succeed the first time. 

Red streaks are often observed on otherwise successful gild- 
ing. These streaks are caused by the iron wire which has 
been wrapped round the article. They disappear by plunging 
the article in dilute nitric acid, or, still better, in pure hydro- 
chloric acid. 

For the sake of completeness, a method of gilding which 
gives to some parts of the article a bright, and to others a 
matt, appearance may here be mentioned. It is a combination 
of fire-gilding with electro-deposition, the matt places being pro- 
duced by the former operation and the bright places by the 
latter. The operation is as follows : The places which are to 
be matt are first gilded with amalgam, heated, scratch-brushed 
and raised. The entire article is then gilded with the assistance 
of the battery, no attention being paid to any gold depositing 
upon the surfaces already gilded. The entire surface is then 
carefully scratch-brushed, and the electro-gilded surfaces are 
next coated with a paste of flake-white, water and glue, and 
then with a thick paste of clay, the fire-gilded surfaces remain- 
ing free. The whole is then allowed to dry, when the fire- 
gilded surfaces are matted by being treated, as above described, 
with a hot paste of saltpetre, common salt and alum. The 
coatings of flake- white and clay are then dissolved by means 
of water acidulated with hydrochloric acid. The only purpose 
of these coatings is to prevent a too intense action of the heat 
upon the electro-gilded portions. The latter, if necessary, are 
24 



370 ELECTRO-DEPOSITION OF METALS. 

then again scratch-brushed, which must, however, be done with 
the greatest care to avoid injury to the matt portions. The 
article is finally polished. 

The following process, however, is better and more con- 
venient: 

The surfaces which are to remain matt are first gilded and 
deadened, and then coated with varnish. When dry the article 
is pickled; the acid does not attack the varnished surfaces. 
The object is then brought into the electro-gilding bath, which 
also does not attack the varnish. When the desired shade of 
gold has been obtained, the article is taken from the bath and 
the varnish removed by means of benzine. The article is then 
washed in a warm potassium cyanide solution, next in boiling 
water, and finally dried. The matt gilding, no matter by which 
process it may have been produced, is only suitable for articles 
not exposed to friction, a slight touch with the fingers being 
sufficient to deprive it of its delicate lustre. 

Old matt gilding may be improved by boiling with potash 
and washing in dilute sulphuric or nitric acid. This suffices 
for the removal of stains caused by grease, smoke or dust. If, 
however, the gilding is worn off, the article has to be scratch - 
brushed and regilt. 

Du Fresne gives a method of gilding, which is also a com- 
bination of fire-gilding with electro-deposition. It is executed 
as follows : 

The articles are galvanized with the assistance of the current, 
in a mercurial solution consisting of cyanide of mercury in 
potassium cyanide, with additions of carbonate and phosphate 
of soda, then gilded in an ordinary gilding bath, next again 
coated with mercury, then again gilded, and so on, until a de- 
posit of sufficient thickness is obtained. The mercury is then 
evaporated over glowing coals, and the articles, after scratch- 
brushing, are burnished. 

According to another process, the articles are gilded in a bath 
consisting of 98 per cent, potassium cyanide 1.2 ozs., cyanide 
of gold 92^ grains, cyanide of mercury 92^ grains, distilled 






DEPOSITION OF GOLD. 37 1 

water i quart, a strong current being used. The articles being 
sufficiently gilded, the mercury is evaporated, the articles 
scratch-brushed and finally polished. 

Removing gold from gilded articles — " Stripping!' — Gilded 
articles of iron and steel are best stripped by treating them as 
anodes in a solution of from 2 to 2){ ozs. of 98 per cent, 
potassium cyanide in 1 quart of water, and suspending a copper 
plate greased with oil or tallow as the cathode. Gilded silver- 
ware is readily stripped by heating to ignition and then im- 
mersing in dilute sulphuric acid, whereby the layer of gold 
cracks off, the heating and subsequent immersion in dilute sul- 
phuric acid being repeated until all the gold is removed. Be- 
fore heating and immersing in dilute sulphuric acid, the articles 
may first be provided with a coating of a paste of sal ammo- 
niac, flowers of sulphur, borax, and nitrate of potash, which is 
allowed to dry. On the bottom of the vessel containing the 
dilute sulphuric acid the gold will be found in laminae and 
scales, which are boiled with pure sulphuric acid, washed, and 
finally dissolved in aqua regia, and made into chloride of gold 
or fulminating gold. 

To strip articles of silver, copper, or German silver which will 
not bear heating, the solution of gold may be effected in a mix- 
ture of 1 lb. of fuming sulphuric acid, 2.64 ozs. of concentrated 
hydrochloric acid, and 1.3 ozs. of nitric acid of 40 BJ. Dip 
the articles in the warm acid mixture and observe the progres- 
sive action of the mixture by frequently removing the articles 
from it. The articles to be treated must be perfectly dry be- 
fore immersing in the acid mixture, and care must be had to 
preserve the latter from dilution with water in order to prevent 
the acids from acting upon the basis-metal. 

Determination of genuine gilding. — Objects apparently gilded 
are rubbed upon the touchstone, and the streak obtained is 
treated with pure nitric acid of 1.30 to 1.35 specific gravity. 
The metal contained in the streak thereby dissolves, and as far 
as it is not gold disappears, while the gold remains behind. 
The stone should be thoroughly cleansed before each operation, 



372 ELECTRO-DEPOSITION OF METALS. 

and the streak should be made not with an edge or a corner of 
the object to be tested, but with a broader surface. If no gold 
remains upon the stone, but there is, nevertheless, a suspicion 
of the article being slightly gilded, proceed with small articles 
as follows : Take hold of the article with a pair of tweezers, and 
after washing it first with alcohol, and then with ether, and 
drying upon blotting paper, pour over it in a test glass, cleansed 
with alcohol or ether, according to the weight of the article, 
0.084 to 5.64 drachms of nitric acid of 1.30 specific gravity free 
from chlorine. The article will be immediately dissolved, and 
if it has been gilded never so slightly, perceptible gold spangles 
will remain upon the bottom of the glass. 

Examination of Gold Baths. 

The determination of free potassium cyanide and of the 
potassium carbonate which is formed, is effected in the same 
manner as given under " Examination of copper baths and of 
silver baths." 

The determination of the gold is effected by the electrolytic 
method. With baths poor in gold, 50 cubic centimeters are 
used for electrolysis, and with baths rich in gold, 25 cubic 
centimeters. After diluting with water to within 1 centimeter 
of the rim of the platinum dish, the liquid is electrolyzed for 
about three hours with a current-density ND 100 = 0.067 
ampere, the complete separation of the gold being recognized 
by a platinum strip suspended over the rim of the dish and 
dipping into the fluid showing in fifteen minutes no trace of a 
separation of gold. 

The dish is then washed, rinsed with alcohol, and dried at 
212° F. To obtain the content of gold in grammes per liter of 
bath, multiply the weight of the precipitate by 20, when 50 
cubic centimeters, or by 40, when 25 cubic centimeters, of the 
bath have been used. 

The content of gold in the baths declines constantly, especi- 
ally with the use of platinum and carbon anodes. For strength- 
ening the baths neutral gold chloride dissolved in potassium 



DEPOSITION OF GOLD. 373 

cyanide is used, 2 grammes neutral gold chloride and 1.4 
grammes 99 per cent, potassium cyanide dissolved in a small 
quantity of water or directly in the bath, being required for every 
gramme of gold deficit in the baths. 

The determination of gold described above is suitable only 
for baths prepared with potassium cyanide, which contain the 
gold in the form of potassium gold cyanide. The determina- 
tion of gold in baths prepared with yellow prussiate of potash 
is more difficult and should be made by a skilled analyst. 

Recovery of gold from gold baths, etc. — To recover the gold 
from old cyanide gilding baths, evaporate the baths to dryness, 
mix the residue with litharge, and fuse the mixture. The gold 
is contained in the lead button thus obtained. The latter is 
then dissolved in nitric acid, whereby the gold remains behind 
in the form of spangles. These spangles are filtered off and 
dissolved in aqua regia. 

The following method is used for the recovery of gold by the 
wet process : The bath containing gold, silver and copper is 
acidulated with hydrochloric acid, which causes a disengage- 
ment of hydrocyanic acid. This gas is extremely poisonous, 
for which reason the operation should be carried on in the open 
air, or where there is a good draught or ventilation to carry off 
the fumes. A precipitate consisting of the cyanides of gold 
and copper and chloride of silver is formed. This is well 
washed and boiled in aqua regia, which dissolves the gold and 
copper as chlorides, leaving the chloride of silver behind. The 
solution containing the gold and copper is evaporated nearly 
to dryness in order to remove the excess of acid, the residue is 
dissolved in a small quantity of water, and the gold precipitated 
therefrom as a brown metallic powder by the addition of sul- 
phate of iron (copperas). The copper remains in solution. 

Finely divided zinc — so-called zinc- dust — is an excellent 
agent for the precipitation of gold in a pulverulent form from 
cyanide gilding baths. By adding zinc-dust to an exhausted 
cyanide gilding bath, and thoroughly shaking or stirring it 
from time to time, all the gold is precipitated in two or three 



374 ELECTRO-DEPOSITION OF METALS. 

days. The quantity of zinc required for precipitation depends 
of course on the quantity of gold present, but generally speak- 
ing, yi lb., or at the utmost I lb., of zinc-dust will be required 
for ioo quarts of exhausted gilding bath. 

The pulverulent gold obtained is washed, treated first with 
hydrochloric acid to remove adhering zinc-dust, and next with 
nitric acid to free it from silver and copper. 

From the acid mixtures serving for matt pickling gold, or 
for stripping, the gold is precipitated by solution of sulphate of 
iron (copperas) added in excess. The gold present is precipi- 
tated as a brown powder mixed with ferric oxide. This powder 
is filtered off and treated in a porcelain dish with hot hydro- 
chloric acid, which dissolves the iron. The gold which remains 
behind is then filtered off, and, after washing, dissolved in aqua 
regia in order to work the solution into fulminating gold or 
neutral chloride of gold. 



CHAPTER XL 

DEPOSITION OF PLATINUM AND PALLADIUM, 
i Deposition of Platinum. 

Properties of platinum. — Pure platinum is white with a gray- 
ish tinge. It is as soft as copper, malleable and very ductile. 
At a white heat it can be welded, but is fusible only with the 
oxyhydrogen blowpipe or by the electric current. Its specific 
gravity is 21.4. 

Air has no oxidizing action upon platinum. It is scarcely 
acted upon by any single acid ; prolonged boiling with con- 
centrated sulphuric acid appears to dissolve the metal slowly. 
The best solvent for it is aqua regia, which forms the tetrachlo- 
ride, PtCl 4 . Chlorine, bromine, sulphur and phosphorus com- 
bine directly with platinum, and fusing saltpetre and caustic 
alkali attack it. 

Besides, in the malleable and fused state, platinum may be 
obtained as a very finely divided powder, the so-called platinum 
blacky which is precipitated with zinc from dilute solution of 
platinum chloride acidulated with hydrochloric acid. 

Platinum baths. — In view of the valuable properties of plat- 
inum of oxidizing only under certain difficult conditions, of pos- 
sessing an agreeable white color, and of taking a fine polish, it 
seems strange that greater attention has not been paid to the 
electro-deposition of this metal than is actually the case. The 
reason for this may perhaps be found in the fact that the baths 
formerly employed for experiments possessed serious defects, 
causing the operator many difficulties, and besides allowed only 
of the production of thin deposits. Giving due consideration 
to the requirements of the process of electro-deposition of plati- 
num, and with the use of a suitable bath, deposits of platinum of 

(375) 



376 ELECTRO-DEPOSITION OF METALS. 

a certain thickness can be readily produced, and necessary con- 
ditions will be described under ■" Treatment of platinum baths." 

The platinum baths formerly proposed did not yield satis- 
factory results, because the content of platinum was too small 
in some of them, while with others dense deposits could not be 
obtained. A more recent formula by Boettger, however, gives 
quite a good bath. A moderately dilute boiling hot solution 
of sodium citrate is added to platoso-ammonium chloride until 
an excess of the latter no longer dissolves, even after continued 
boiling. The following proportions have been found very 
suitable: Dissolve i7^ozs. of citric acid in 2 quarts of water, 
and neutralize with caustic soda. To the boiling solution add, 
whilst constantly stirring, the platoso-ammonium chloride 
freshly precipitated from 2.64 ozs. of chloride of platinum, 
heat until solution is complete, allow to cool, and dilute with 
water to 5 quarts. To decrease the resistance of the bath, 0.7 
or 0.8 oz. of sal ammoniac may be added ; a larger addition, 
however, will cause the separation of dark- colored platinum. 

The platoso-ammonium chloride is prepared by adding to a 
concentrated solution of chloride of platinum concentrated 
solution of sal ammoniac until a yellow precipitate is no longer 
formed on adding a further drop of sal ammoniac. The pre- 
cipitate is filtered off and brought into the boiling solution of 
sodium citrate. This bath works very uniformly if the content 
of platinum is from time to time replenished. 

"The Bright Platinum Plating Company," of London, has 
patented the following composition of a platinum bath: Chlor- 
ide of platinum 0.98 oz., sodium phosphate 19% ozs., ammo- 
nium phosphate 3.95 ozs., sodium chloride 0.98 oz., and borax 
0.35 oz., are dissolved, with the aid of heat, in 6 to 8 quarts of 
water, and the solution is boiled for 10 hours, the water lost by 
evaporation being constantly replaced. The results obtained 
with this bath were not much better than with Bottger's. 

Dr. W. H. Wahl gives the following directions for preparing 
platinum baths:* 

♦Journal of the Franklin Institute, July, 1890. 



DEPOSITION OF PLATINUM AND PALLADIUM. 377 

Alkaline platinate bath. — Platinic hydrate, 2 ozs. ; caustic 
potassa (or soda), 8 ozs.; distilled water, 1 gallon. 

Dissolve one-half of the caustic potassa in a quart of distilled 
water, add to this the platinic hydrate in small quantity at a 
time, facilitating solution by stirring with a glass rod. When 
solution is effected, stir in the other half of alkali dissolved in a 
quart of water ; then dilute with enough distilled water to form 
one gallon of solution. To hasten solution, the caustic alkali 
may be gently heated, but this is not necessary, as the platinic 
hydrate dissolves very freely. This solution should be worked 
with a current of about two volts, and will yield metal of an 
almost silvery whiteness upon polished surfaces of copper and 
brass, and quite freely. There should be slight, if any, percep- 
tible evolution of hydrogen at the cathode, but a liberal evolu- 
tion of oxygen at the anode. An addition of a small proportion 
of acetic acid to this bath improves its operation where a heavy 
deposit is desired. The anode must be of platinum or carbon, 
and owing to the readiness with which the metal is deposited, 
an excess of anode-surface is to be avoided. Articles of steel, 
nickel, tin, zinc, or German silver will be coated with black and 
more or less non-adherent platinum ; but by giving objects of 
these metals a preliminary thin electro-deposit of copper in the 
hot cyanide bath they may be electro- platinized in the alkaline 
platinate bath equally as well as copper. The bath may be 
worked hot or cold, but it is recommended to work it at a tem- 
perature not exceeding ioo° F. It may be diluted to one-half 
the strength indicated in the formula and still yield excellent 
results. The surface of the objects should be highly polished 
by buffing or otherwise prior to their introduction into the bath, 
if the resulting deposit is designed to be brilliant. 

The deposition of platinum takes place promptly. In five 
minutes a sufficiently heavy coating will be obtained for most 
purposes. The deposited metal is so soft, however, that it re- 
quires to be buffed very lightly. A heavier deposit will appear 
gray in color, but will accept the characteristic lustre of plati- 
num beneath the burnisher. 



378 ELECTRO-DEPOSITION OF METALS. 

An oxalate solution is prepared by dissolving I oz. of platinic 
hydrate in 4 ozs. of oxalic acid and diluting the solution to the 
volume of one gallon with distilled water. The solution should 
be kept acidified by the occasional addition of some oxalic acid. 
The simplest plan of using this bath, which requires no atten- 
tion to proportions, is simply to work with a saturated solution 
of the oxalate, keeping an undissolved excess always present at 
the bottom of the vessel. An addition of a small quantity of 
oxalic acid now and then will be found advantageous. The 
double salts of oxalic acid with platinum and the alkalies may 
be formed by saturating the binoxalate of the desired alkali 
with platinic hydrate and maintaining the bath in normal 
metallic strength by the presence of an undissolved residuum 
of platinous oxalate. 

The double oxalates are not so soluble in water as the simple 
salt. The oxalate baths, both of single and double salts, may be 
worked cold or hot (though not to exceed 150 F.) with a 
current of comparatively low pressure. The metal will deposit 
bright, reguhne and adherent on copper and brass. Other 
metallic objects must receive a preliminary coppering as above. 
The deposited metal is dense, with a steely appearance, and 
can be obtained of any desired thickness. 

The deposit obtained in the oxalate bath is sensibly harder 
than that from the alkaline platinate bath, and will bear buffing 
tolerably well. 

The phosphate bath may be prepared by the following 
formula : 

Phosphoric acid, syrupy (specific gravity 1.7), 8 ozs., plati- 
nic hydrate 1 to 1^ ozs., distilled water 1 gallon. 

The acid should be moderately diluted with distilled water 
and the solution of the hydrate effected at the boiling tempera- 
ture. Water should be added cautiously from time to time to 
supply that lost by evaporation. When solution has taken 
place, the same should be diluted with sufficient water to make 
the volume 1 gallon. The solution may be worked cold or 
heated to 1 00° F., and with a current much stronger than that 



DEPOSITION OF PLATINUM AND PALLADIUM. 379 

required for the platinates and oxalates. The ammonio (and 
sodio) platinic phosphates may be formed from the simple 
phosphate by carefully neutralizing the solution of the phos- 
phate with ammonia (or soda) ; then adding an excess of 
phosphoric acid, or enough to dissolve the precipitate formed, 
and an additional quantity to insure a moderate amount of free 
phosphoric acid in the bath. The phosphate baths will be 
maintained of normal strength by additions of platinic hydrate, 
the solutions of which will need to be assisted by heating the 
bath, preferably at the close of each day's work. The metal 
yielded by the electrolysis of these phosphate solutions is 
brilliant and adherent. It has the same steely appearance as 
that exhibited by the oxalate solutions, but to a less pro- 
nounced degree. The physical properties of the deposited 
metal are in other respects like those described in connection 
with that obtained from the oxalate baths. 

Management of platinum baths. Copper and brass may be 
directly plated with platinum, but iron, steel and other metals 
are first to be coppered, otherwise they would soon decompose 
the platinum bath, independent of the fact that an unexcep- 
tionable deposit cannot be produced upon them without the 
cementing intermediary layer of copper. 

Platinum baths must be used hot, and even then require a 
current of 5 to 6 volts, and hence, in plating with a battery at 
least three, or better four, Bunsen elements must be coupled, 
one after the other, for tension. An abundant evolution of gas 
must appear on the objects and anodes. The anode-surface 
(platinum anodes) must not be too small, and should be only 
at a few centimeters distance from the objects. Since the 
platinum anodes do not dissolve, the content of platinum in the 
bath decreases constantly, and the bath must from time to time 
be strengthened. For this purpose, the bath, prepared accord- 
ing to Boettger's formula, is heated in a porcelain dish or enam- 
eled vessel to the boiling point, a small quantity of fresh solu- 
tion of sodium citrate is added and platoso-ammonium chloride 
introduced so long as solution takes place. A concentrated 



380 ELECTRO-DEPOSITION OF METALS. 

solution of platoso-ammonium chloride in sodium citrate (so- 
called platinum essence) may be kept on hand and a small 
quantity of it be at intervals added to the bath. Baths pre- 
pared according to the English method are strengthened by 
the addition of platinum chloride. 

Execution of platinum-plating. — The objects thoroughly 
freed from grease and, if necessary, coppered, are suspended 
in the bath heated to between 176 and 194 F., and this tem- 
perature must be maintained during the entire operation. The 
current should be of sufficient strength and the anodes placed 
so close to the objects that a liberal evolution of gas appears 
on them. For plating large objects, it is recommended to go 
round them, at a distance of 0.31 to 0.39 inch, with a hand- 
anode of platinum sheet, which should not be too small and 
should be connected to the anode-rod. When the current has 
vigorously acted for 8 to 10 minutes, the objects are taken from 
the bath, dried, and polished. However, for the production of 
heavy deposits — for instance, upon points of lightning-rods — < 
the deposit is vigorously brushed with a steel-wire scratch- 
brush or fine pumice-powder. The objects are then once more 
freed from grease and returned for 10 or 15 minutes longer to 
the bath to receive a further deposit of platinum with a weaker 
current, -which must, however, be strong enough to cause the 
escape of an abundance of gas-bubbles. The objects are then 
taken out, and after immersion in hot water, dried in sawdust. 
The deposit is then well burnished, first with the steel tool and 
finally with the stone, whereby the gray tone disappears and 
the deposit shows the color and lustre of massive platinum 
sheet. Points of lightning-rods platinized in this manner were 
without flaw after an exposure to atmospheric influences for 
more than six years. 

Platinizing of glass. — Glass may be platinized by means of 
the galvanic current as follows : Dissolve 14 drachms of platinic 
hydrate in 17% ozs. of a 10 per cent, solution of caustic soda 
or potash. Add to the solution 17^ ozs. more of the alkali 
solution and dilute with water to 2 quarts. The temperature 



DEPOSITION OF PLATINUM AND PALLADIUM. 38 1 

of the bath should not exceed ioo° F., and the strength of the 
current should be two volts. 

Platinizing by contact. — Though a thick deposit cannot be 
produced by the contact-process, Fehling's directions may here 
be mentioned as suitable for giving a thin coat of platinum to 
fancy articles. He recommends a solution of 5.64 drachms of 
chloride of platinum and 7 ozs of common salt in 1 quart of 
water, which is made alkaline by the addition of a small quan- 
tity of soda lye, and for use heated to the boiling point. 

If larger articles are to be platinized by contact, free them 
from grease, and after pickling, and if necessary, coppering, 
wrap them round with zinc wire, or place them upon a bright 
zinc sheet, and introduce them into the heated bath. All the 
remaining manipulations are the same as in other contact pro- 
cesses. 

Recovery of platinum from platinum solutions. — From not 
too large baths, precipitation of the platinum with sulphuretted 
hydrogen is the most suitable method, and preferable to evap- 
orating and reducing the metal from the residue. The process 
is as follows : Acidulate the platinum solution with hydrochloric 
acid, and, after warming it, conduct sulphuretted hydrogen into 
it. The metal (together with any copper present) precipitates 
as sulphide of platinum. The precipitate is filtered off, dried, 
and ignited in the air, whereby metallic platinum remains be- 
hind. From larger baths the platinum may be precipitated by 
suspending bright sheets of iron in the acidulated bath. In 
both cases the precipitated platinum is treated with dilute nitric 
acid in order to dissolve any copper present. After filtering 
off and washing the pure platinum, dissolve it in aqua regia. 
The solution is then evaporated to dryness in the water bath, 
and the chloride of platinum thus obtained may be used in 
making a fresh bath. 

2 Deposition of Palladium. 

Properties of palladium. — Palladium, when compact, has a 
white color and possesses a lustre almost equal to that of silver. 



382 ELECTRO-DEPOSITION OF METALS. 

Its specific gravity is about 12.0; it is malleable and ductile, 
and may be fused at a white heat. In the oxy-hydrogen flame 
it is volatilized, forming a green vapor. It is less permanent in 
the air than platinum. It is dissolved by nitric acid ; it is 
scarcely attacked, however, by hydrochloric or sulphuric acid. 
Hydriodic acid and free iodine coat it with the black palladium 
iodide. 

On account of the high price of its salts, palladium has been 
but little used for electro-plating purposes; nor for, the same 
reason, is it likely to be more extensively employed in the 
future. 

According to M. Bertrand, the most suitable bath consists of 
a neutral solution of the double chloride of palladium and 
ammonium, which is readily decomposed by 3 Bunsen elements 
coupled one behind the other (therefore about 5.4 volts). A 
sheet of palladium is used as anode. 

A solution of palladium cyanide in potassium cyanide does 
not yield as good results as the above bath. 

Palladium is entirely constant in the air, and in color closely 
resembles silver. It possesses further the property of not 
being blackened by sulphuretted hydrogen, and for this reason 
it is sometimes employed for coating silver-plated metallic 
articles. 

Palladium has also of recent years been employed for plat- 
ing watch movements. According to M. Piiet, 4 milligrammes 
(about yV grain) of palladium are sufficient to coat the works of 
an ordinary sized watch. M. Pilet recommends the following 
bath: Water 2 quarts, chloride of palladium 5^ drachms, 
phosphate of ammonia 3J^ ozs., phosphate of soda 17 % ozs., 
benzoic acid 2^ drachms. 

Deposits of iridium and rhodium have recently been pro- 
duced from baths similar in composition to those mentioned 
under palladium. But as these metals would be used for plat- 
ing purposes only in isolated cases, it is not necessary to enter 
into details. 



CHAPTER XII. 

DEPOSITION OF TIN, ZINC, LEAD, AND IRON. 
I. DEPOSITION OF TIN. 

Properties of tin. — Tin is a white, highly lustrous metal. It 
possesses but little tenacity, but has a high degree of mallea- 
bility, and tin-foil may be obtained in leaves less than ^tri of 
a millimetre in thickness. Tin melts at about 446° F. and 
evaporates at a high temperature. The fused metal shows 
great tendency to crystallize on congealing. By treating the 
surface of melted tin with a dilute acid, the crystalline structure 
appears as designs {moire metalliqne), resembling the ice- 
flowers on frosted windows. 

Tin remains quite constant even in moist air, and resists the 
influence of an atmosphere containing sulphuretted hydrogen. 
Strong hydrochloric acid quickly dissolves tin on heating, 
hydrogen being evolved and stannous chloride being formed. 
Dilute sulphuric acid has but little action on the metal ; when 
heated with concentrated sulphuric acid, sulphur dioxide is 
evolved. Dilute nitric acid dissolves tin in the cold without 
evolution of gas ; concentrated nitric acid acts vigorously upon 
the metal, whereby oxide of tin, which is insoluble in the acid, 
is formed. Alkaline lyes dissolve the metal to sodium stannate, 
hydrogen being thereby evolved. 

Tin baths. The bath used by Roseleur for tinning with the 
battery works very well. It is composed as follows : 

I. Pyrophosphate of soda 3.5 ozs., tin-salt (fused) 0.35 oz., 
water 10 quarts. To prepare the bath dissolve the pyrophos- 
phate of soda in 10 quarts of rain water, suspend the tin-salt in 
a small linen bag in the solution, and move the bag to and fro 
until its contents are entirely dissolved. 

(383) 



,84 ELECTRO-DEPOSITION OF METALS. 



rets of zinc, copper, and brass are directly tinned in this 
bath with a current of slight tension. Articles of iron and steel 
are first coppered or preliminarily tinned in a bath prepared 
according to formula VIII., the deposit of tin being then aug- 
mented in bath I. with the battery current. Cast-tin anodes as 
large as possible are used, which, however, will not keep the 
content of tin in the bath constant. It is, therefore necessary, 
from time to time, to add tin-salt, which is best done by pre- 
paring a solution of 3.5 ozs. of pyrophosphate of soda in 1 
quart of water and introducing into the solution tin-salt as long 
as the latter dissolves clear. Of this tin essence add to the 
bath more or less, as may be required, and also augment the 
content of pyrophosphate of soda, if, notwithstanding the addi- 
tion of tin-salt, the deposition of tin proceeds sluggishly. 

Though the bath composed according to formula I. suffices 
for most purposes, an alkaline tin bath, first proposed by 
Eisner, and later on recommended by Maistrasse, Fearn, Birg- 
ham, and others, with or without addition of potassium cyanide, 
may be mentioned as follows: — 

II. Crystallized tin-salt 0.7 oz., water 1 quart, and potash 
lye of io° Beaume until the precipitate formed dissolves. 

As seen from the formula the solution of tin-salt is com- 
pounded with potash lye of the stated concentration (or with a 
solution of 1 oz. of pure caustic potash in water;, until the pre- 
cipitate of stannous hydrate again dissolves. 

Some operators recommend the addition of 0.35 oz. of potas- 
sium cyanide to the solution. 

Without potassium cyanide the bath requires 3.75 to 4 volts, 
and with it, 3.5 volts. 

In testing Salzede's bronze bath (p. 292), it was found to 
yield quite a good deposit of tin directly upon cast-iron, and it 
was successfully used for this purpose by omitting the cuprous 
chloride and using 14. 11 drachms of stannous chloride, so that 
the composition became as follows : 

Ha. 98 per cent, potassium cyanide 3.5 ozs., carbonate of 
potassium 3S/i ozs., stannous chloride 14.1 1 drachms, water 10 
quarts. With 4 volts a heavy deposit was rapidly obtained. 



DEPOSITION OF TIN, ZINC, LEAD, AND IRON. 385 

III. A tin bath of stannous chloride, caustic soda and potas- 
sium cyanide, given by Pfanhauser, contains 1 1 % drachms of 
stannous chloride, equal to about J% drachms of metallic tin 
per quart. It is still more advantageous to use double the 
quantity of tin, the composition of the bath being then as 
follows : 

Water 10 quarts, fused stannous chloride 14 ozs., caustic 
soda 17^2 ozs., 100 per cent, potassium cyanide 3^ ozs. 

The bath, as above composed contains about 15 drachms of 
metallic tin per quart, and with 3^ volts furnishes a deposit of 
tin of about 4^ grains per hour. 

Pfanhauser has made new experiments and found that still 
more favorable results are obtained with a solution of 1 Y / 2 ozs. 
of stanno-ammonium chloride in 1 quart of water, a deposit of 
9^ grains of tin per hour being obtained with a current of 
only 1 y 2 volts. 

The solution of the salt is readily effected. Cast-tin anodes 
are to be used. 

The temperature of the bath should be between 68° and JJ° 
F. In case the bath becomes poor in metal, stanno-ammonium 
chloride is added. 

The deposit of tin is rather rough, but can be readily made 
bright by treatment with brass scratch-brushes. 

IV. A tin bath given by Taucher is composed as follows : 
Water 500 quarts, sodium or pyrophosphate 11 lbs., crys- 
tallized tin-salt 21 ozs., or, still better, fused tin salt 17^ ozs. 

Bring the water into a tank completely lined with plates or 
anodes of tin joined together and connected with the positive 
pole wire. Dissolve the pyrophosphate in the water, stirring 
constantly. Place the tin-salt in a copper sieve, and immerse 
the latter about one-half in the solution ; an abundant milky 
turbidity is immediately formed, which, however, disappears on 
stirring. When all the tin-salt is dissolved, remove the sieve, 
and the tin-bath, which now forms a clear fluid, either color- 
less or of a slightly yellowish color, is ready for use, it being 
only necessary to secure the articles to be tinned to the rods 
25 



386 ELECTRO-DEPOSITION OF METALS. 

connected with the negative pole. The anodes do not suffice 
to keep the bath saturated, and hence, when the deposit be- 
comes weaker, small quantities of equal parts of tin-salt and of 
sodium pyrophosphate have to be added. The solution of 
these salts should always be effected with the assistance of a 
sieve to prevent small pieces of tin-salt from falling to the 
bottom of the bath, where they would be enveloped by an al- 
most insoluble crust and remain nearly unchanged. 

This tin bath is suitable for all kinds of metals, the deposit 
obtained combining, with considerable solidity, a matted and 
white appearance closely resembling silver. 

Management of tin baths. — Tin baths should not be used at a 
temperature below 68° F. They require (formulae I. and II.), 
according to their composition, a current of 2 to 3 volts, so that 
two Bunsen elements coupled one after the other suffice for all 
purposes. Too strong a current causes a pulverulent reduction 
of the tin, which does not adhere well, while with a suitable 
current-strength quite a dense and reguline deposit is obtained. 
Cast-tin plates with as large a surface as possible are used as 
anodes. The choice of the tin-salt exerts some influence upon 
the color of the tinning. By using, for instance, crystallized 
tin-salt, which is always acid, in preparing the bath according 
to formula I., a beautiful white tinning with a bluish tinge is 
obtained, which, however, does not adhere so well as that pro- 
duced with fused tin-salt. Again, the latter yields a somewhat 
dull gray layer of tin, and, therefore, the effects of the bath will 
have to be corrected by the addition of one or the other salt. 

As previously mentioned, iron and steel objects are best sub- 
jected to a light preliminary tinning by boiling in the bath VIII. 
However, instead of this preliminary tinning, they may first be 
electro-coppered and, after scratch-brushing the copper de- 
posit, brought into the tin bath. 

When the action of the bath becomes sluggish, it has to be 
refreshed (for formula I. ) by the addition of tin-salt and pyro- 
phosphate of soda, or (for formula II.) by the addition of pot- 
ash lye and tin-salt. 



DEPOSITION OF TIN, ZINC, LEAD, AND IRON. 387 

Process of tin-plating. — From what has been said, it will be 
evident that the execution of tin-plating is simple enough. 
After being freed from grease and pickled, the objects are 
brought into the bath and plated with a weak current. For 
heavy deposits the objects are frequently taken from the bath 
and thoroughly brushed with a brass scratch-brush, not too 
hard, and moistened with dilute sulphuric acid ( 1 part acid 
of 66° Be. to 25 water) and, after rinsing in water, are re- 
turned to the bath. If, with the use of too strong a current, 
the color of the deposit is observed to turn a dark dull gray, 
scratch-brushing must be repeated. When the tinning is fin- 
ished the articles are brushed with a brass scratch-brush and 
decoction of soap-root, then dried in sawdust, and polished 
with fine whiting. 

Tinning by contact a?id boiling. — For tinning by zinc-contact 
in the boiling tin bath the following solutions may be recom- 
mended : 

V. According to Gerhold : Pulverized tartar and alum, of 
each 3.5 ozs., fused stannous chloride 14 drachms, rain-water 
10 quarts. 

VI. According to Roseleur : Potassium pyrophosphate 7 ozs., 
crystallized stannous chloride (tin-salt), 11 drachms, fused stan- 
nous chloride 2.8 ozs., rain-water 10 quarts. 

VII. According to Roseleur, for tinning by immersion : Potas- 
sium pyrosphate 5.6 ozs., fused stannous chloride 1.23 ozs., 
rain water 10 quarts. 

Formulae V. and VI. yield good results. For tinning by con- 
tact, heat the bath to boiling and suspend the clean and pickled 
objects in contact with pieces of zinc, or, better, wrapped around 
with zinc wire spirals, care being had from time to time to shift 
them about to prevent staining. Large baths which cannot be 
readily heated are worked cold, the objects being covered with 
a large zinc plate. In the cold bath the formation of the tin 
deposit requires, of course, a longer time. By using the electric 
current the deposit can be made as heavy as desired. By im- 
mersion in the bath prepared according to formula VII., zinc 



3<S8 ELECTRO-DEPOSITION OF METALS. 

can only be coated with a very thin film of tin, which, however, 
by the use of a battery, can be made as heavy as desired. 

For tinning by contact in a cold bath, Zilken has patented 
the following solution: Dissolve with the aid of heat in ioo 
quarts of water, tin-salt 7 to 10.5 ozs., pulverized alum 10.5 
ozs., common salt 15^ ozs., and pulverized tartar 7 ozs. The 
cold solution forms the tin bath. The objects to be tinned are 
to be wrapped round with strips of zinc. Duration of the pro- 
cess 8 to 10 hours. 

VIII. Tinning solution for iron and steel articles. — Crystal- 
lized ammonium-alum 7 ozs., crystallized stannous chloride 2.8 
drachms, fused stannous chloride 2.8 drachms, rain-water 10 
quarts. Dissolve the ammonium-alum in the hot water, and 
when dissolved add the tin-salts. The bath is to be used boil- 
ing hot and kept at its original strength by an occasional addi- 
tion of tin-salt. The clean and pickled iron objects, after being 
immersed in the bath, become in a few seconds coated with a 
firmly adhering film of tin of a dead, white color, which may 
be polished by scratch-brushing or scouring with sawdust in 
the tumbling-barrel. Tinning by boiling in this bath is the 
most suitable preparation for iron and steel objects, which are 
to be provided with a heavy electro-deposit of tin. To be 
entirely sure of success it is recommended thoroughly to 
scratch-brush the objects, then to return them once more to 
the bath, and finally to suspend them in a bath composed ac- 
cording to formula I. or II. 

A tinning solution for small brass and copper articles (pins, 
eyes, hooks, etc.), consists of a boiling solution of: Pulverized 
tartar 3.5 ozs., stannous chloride (tin- salt) 14. u drachms, 
water 10 quarts. After heating the bath to the boiling-point, 
immerse the objects to be tinned in a tin sieve or in contact 
with pieces of zinc in a stoneware sieve. Frequent stirring 
with a tin rod shortens the process. 

Another solution, given by Bottger, also yields good results : 
Dissolve oxide of tin by boiling with potash lye, and place the 
copper or brass objects to be tinned in the boiling solution in 
contact with tin shavings. 



DEPOSITION OF TIN, ZINC, LEAD, AND IRON. 389 

Eisner s bath yields equally good results. It consists of a 
solution of equal parts of tin-salt and common salt in rain-water. 
The manipulation is the same as given above. 

A durable coating of tin is also produced with the use of 
potassium stannate, which is prepared as follows: Tin is 
melted and then granulated by pouring it into water. The 
granulated tin is brought into a vessel of glass or porcelain, 
and crude nitric acid poured over it, whereby, with strong 
effervescence of the fluid and the evolution of brown-red 
vapors, it is converted into a white powder consisting of stan- 
nic oxide. The latter is separated from the unchanged tin by 
washing with water and dried. The dry powder is mixed with 
pure potash in the proportion of 3 parts stannic oxide and 4 
parts potash. The mixture is melted in an iron crucible and 
the fused mass poured upon a stone slab. It consists of 
potassium stannate and is dissolved in boiling water. Potas- 
sium stannate may also be prepared by adding to a solution of 
tin-salt in water, aqua ammonia so long as a precipitate is formed. 
The mass is then allowed to drain off upon a linen cloth and 
repeatedly washed with water. The residue, consisting of 
stannous hydrate, is boiled with strong potash lye, and the 
solution of potassium stannate thus obtained diluted with water. 

Needles are tinned by spreading them out upon a sieve and 
immersing the latter in the bath; larger articles are touched 
with a tin rod while in the bath. The temperature of the bath 
should be between 122 and 21 2° F. Larger articles of brass 
or bronze are best coppered previous to tinning by wrapping 
them with iron wire and immersing them in dilute sulphuric 
acid for a short time ; hydrochloric acid may be substituted 
for the sulphuric acid. 

Tinning may also be effected by dissolving 1 part tin-salt in 
10 parts water, adding to the solution one of 2 parts of caustic 
potash in 20 of water, and stirring until the fluid is clear. The 
articles to be tinned are placed upon a tin plate. The latter is 
brought into the hot bath and touched on several places with 
tin rods. 



390 ELECTRO -DEPOSITION OF METALS. 

To give articles of brass, copper or iron a thin, superficial 
coating of tin, dip them in a solution of tin-salt in which gran- 
ulated tin has been lying for some time, then dust them with 
tin-powder, rub them with a woollen rag, and repeat the opera- 
tion until the article appears tinned. 

A characteristic method of tinning by Stolba is as follows : 
Prepare a solution of 1.75 ozs. of tin-salt and 5.64 drachms of 
pulverized tartar in one quart of water ; moisten with this 
solution a small sponge and dip the latter into pulverulent zinc. 
By then rubbing the thoroughly cleansed and pickled articles 
with the sponge, they immediately become coated with a film 
of tin. To obtain uniform tinning, the sponge must be re- 
peatedly dipped now into the solution and then into the zinc- 
powder, and the rubbing continued for a few minutes. 

For coloring and patinizing tin, see special chapter. 

2. Deposition of Zinc. 

Properties of Zinc. — Zinc is a bluish-white metal, possessing 
high metallic lustre. It melts at 776 F. At the ordinary 
temperature zinc is brittle, but it is malleable at between 21 2° 
and 300 F., and can be rolled into sheets. At 392 F. it 
again becomes brittle and may be readily reduced to powder. 
The specific gravity of zinc varies from about 6.86 to 7.2. 
When strongly heated in the air or in oxygen it burns with a 
greenish-white flame, producing dense white fumes of the 
oxide. 

In moist air it becomes coated with a thin layer of basic 
carbonate, which protects the metal beneath from further 
oxidation. Pure zinc dissolves slowly in the ordinary mineral 
acids, but the commercial article containing foreign metals is 
rapidly attacked, hydrogen being evolved. 

Since zinc is a very electro-positive metal, it precipitates 
most of the heavy metals from their solutions, especially cop- 
per, silver, lead, antimony, arsenic, tin, cadmium, etc., this being 
the reason why in dissolving impure zinc the admixed metals 
do not pass into solution so long as zinc in excess is present. 



DEPOSITION OF TIN, ZINC, LEAD, AND IRON. 39 1 

Caustic alkalies also dissolve zinc, an oxide and free hydrogen 
being formed, especially when it is in contact with a more 
electro-negative metal. 

Zinc in contact with iron protects the latter from rust, and 
also prevents copper from dissolving when in contact with it. 

Zinc baths. — Although most metals can be readily plated 
with a thin, firmly-adhering layer of zinc, the production of 
uniform deposits of pure zinc upon large shaped articles is at- 
tended with difficulties, because zinc baths do not work quite 
well in the deeper portions. Better results are obtained in 
plating articles with depressions by depositing not pure zinc, 
but zinc in combination with other metals. Of course, zinc 
must be largely in excess if the deposit is to have the same 
effect as pure zinc in protecting the plated article from rust. 
By the addition of salts of magnesium and aluminium to the 
zinc bath, Schaag, Dr. Alexander and others have endeavored 
to deposit zinc in combination with these metals. While the 
possibility of depositing aluminium from aqueous solutions is 
doubtful, it is very likely that in Schaag's as well as in Dr. 
Alexander's patented process neither the magnesium nor the 
aluminium is the effective agent, but the tin or mercury salts 
which are also added to the bath. But such additions are 
nothing new, since deposits of zinc-tin alloys with or without 
mercury salts have for many years been produced. The same 
object is attained by an addition of tin and nickel to the zinc 
bath, and experiments have conclusively shown that deposits 
upon iron produced in such a bath protect the iron from rust 
as well as a deposit produced in a bath of pure zinc, or in Dr. 
Alexander's patented zinc baths. 

Below the pure zinc baths mostly used are given : 

I. Sulphate of zinc (white vitriol) 2.8 ozs., ammonium sul- 
phate 1 j£ ozs., sal ammoniac 1 1 drachms, water 1 quart. Dis- 
solve the salts in the heated water and use the bath at 68° F. 
The current-strength should only be slightly greater than 
necessary for the decomposition of the bath. The current of 
two Bunsen elements coupled one after the other is quite too 



39 2 ELECTRO-DEPOSITION OF METALS. 

strong, and must, therefore, be suitably weakened by the re- 
sistance-board. 

As anodes, rolled zinc sheets of not too small dimensions 
are to be used. This bath is suitable for a thick deposit upon 
objects (^sheets and plates) of wrought- and cast-iron, steel, and 
all other metals, but not for plating hollow articles if anodes 
cannot at equal distances be placed around them. The most 
suitable tension is 2.8 to 3 volts. 

II. Caustic potash 2 ozs., chloride of zinc 5^ drachms, sal 
ammoniac 1 1 drachms, water 1 quart. Dissolve the caustic 
potash in one-half of the water, and the chloride of zinc and 
sal ammoniac in the other half, and mix both solutions, stir- 
ring constantly. The result is a clear fluid, which requires a 
current of 2.5 to 3 volts for its decomposition. In consequence 
of the action of the caustic potash upon the sal ammoniac, this 
bath evolves ammonia, the odor of which is very annoying. 
Experiments have proved that plating of cast-iron in this bath 
is not successful. Zinc sheets are used as anodes. In this bath 
the deposit upon shaped articles proceeds better than in the 
preceding, though frequent turning of the objects is required. 

III. Alum 2>H ozs -> hydrated oxide of zinc 5^ drachms, 
water 1 quart. Dissolve 14 drachms of sulphate of zinc in 1 
pint of water, and carefully add potash lye until a further drop 
of it no longer produces a precipitate. Since potash lye dis- 
solves the hydrated oxide of zinc, an excess has to be avoided. 
The precipitate is filtered off, washed with water, and the hy- 
drated oxide of zinc, while still moist, is heated together with 
the solution of 3^ ozs. of alum in 1 quart of water, whereby 
it is completely dissolved. This bath requires a current of 3 
to 3.5 volts. 

IV. Sulphate of zinc (white vitriol) 2.8 ozs., water 1 quart, 
and potash lye sufficient so redissolve the precipitated hy- 
drated oxide of tin. This bath also works quite well, and re- 
quires from 2.75 to 3 volts and 1.5 amperes per i$}4 square 
inches. 

Solution of cyanide of zinc in potassium cyanide may also 



DEPOSITION OF TIN, ZINC, LEAD, AND IRON. 393 

be used for zinc-plating, such a bath having been warmly 
recommended by some authors. However, the production of 
deposits of some thickness requires a long time, and the deposit 
itself shows a tendency to peel off. 

Execution of zinc-plating. — Next to thorough cleansing and 
pickling the objects, especially iron castings, and regulating 
the current, zinc-plating depends on the frequent turning and 
changing the objects in the bath, since the deposit is chiefly 
formed upon the portions nearest to the anodes, and not at 
all, or with difficulty, upon the portions away from the anodes. 
If, notwithstanding frequent changing, some portions do not 
acquire a deposit, recourse must be had, as in nickeling, to the 
hand anode. Next to frequently changing the articles in the 
bath, it is recommended to scratch-brush them several times, 
especially if heavy deposits are to be produced. It is also ad- 
visable to somewhat heat the baths, if possible. 

It is of advantage to superficially zinc iron objects by a 
combined process of contact and boiling, and then to augment 
the layer of zinc in the bath. 

After thorough scratch brushing with a steel brush, not too 
hard, and a decoction of soap-root, the zincked objects are 
rinsed in lime-water, then plunged into hot water, and dried 
in saw-dust. Polishing is effected upon soft cloth bobs with 
Vienna lime and oil. 

Zinc-plating of wrought-iron objects, girders, L-iron, T-iron, 
etc. — For this purpose, Pfanhauser gives the following direc- 
tions. By way of introduction it may be observed that under 
this heading will be considered the plating with zinc of 
wrought-iron objects of considerable length and width. It is 
generally sought to protect such objects from rust by a coat of 
oil paint, but it is well known that such protection does not 
last very long, and the coat of paint has to be renewed every 
year, or at least every second or third year. 

However, for such objects as are used in the construction of 
bridges, etc., a good deposit of zinc is a guarantee for long 
durability, and in constructions where the coat of paint cannot 



394 



ELECTRO-DEPOSITION OF METALS. 



be renewed or repaired, such deposit is of immense value. For 
solidly plating with zinc such larger objects, Pfanhauser recom- 
mends the following bath : 

Water I quart, zinc sulphate 6% ozs., ammonium sulphate 
I ^ ozs. Temperature of the bath, 59 to 68° F. ; concentra- 
tion, 1 4}4° Be. 

The bath is prepared as follows : 

After having decided how many gallons of bath are to be 
prepared, dissolve in one quarter of the quantity of water re- 
quired (best warm) the zinc sulphate, and in one-half of the total 
quantity of water, the ammonium sulphate. The solution of 

Fig. 139. 




the ammonium sulphate may be effected in the plating vat 
itself, but the zinc sulphate has to be dissolved in a special 
vessel indifferent to changes in temperature. When all the 
ammonium sulphate is dissolved, pour in the zinc sulphate 
solution, whilst constantly stirring, and finally add the last 
quarter of the required quantity of water. The bath works 
well at once, without boiling or previous working through with 
the current. 

The objects are best cleansed by means of the sand blast. 

A profile anode corresponding to the shape of the article to 
be plated is to be used, and it is so arranged in the bath that 
all parts of the object are approximately at the same distance 



DEPOSITION OF TIN, ZINC, LEAD, AND IRON. 395 

from it. Fig. 139, for instance, shows the arrangement of the 
anode in zincking a simple girder. 

Zincking of nails, screws, etc. — Such articles are zincked in 
a capacious wire basket which is horizontally suspended, or in 
a revolving drum. Cleaning in alkaline solutions and pickling 
is troublesome and not practicable, because after being for a 
short time exposed to the air the objects commence to rust. 
Hence, it is best to scour them (best dry) in a tumbling barrel 
partially filled with quartz sand or emery powder. When 
working on a large scale the sand blast shown in Fig. 87, p. 
140, may be used to advantage. 

A suitable bath for zincking nails, screws, etc., is composed 
as follows: Water 10 quarts, zinc sulphate 35 ozs., ammonium 
chloride S}4 ozs., ammonium citrate 14 ozs. Temperature of 
the bath, 59 to 68° F. ; concentration of the bath, io}4° Be. 

Zinc plates 0.19 to 0.39 inch thick are to be used as anodes.. 

As previously mentioned, better results are obtained with all 
zinc baths by heating them to from 104 to 122° F. In baths 
thus heated, very voluminous objects, short pipes, larger iron 
castings, etc., have been successfully plated with the use of 
level anodes, which in cold baths could have been effected 
only with great difficulty and by employing special precaution- 
ary measures. 

For zincking iron by contact quite a concentrated solution of 
chloride of zinc and sal ammoniac in water is required. The 
objects are placed in the solution in contact with large surfaces 
of zinc. 

To coat brass and copper with a bright layer of zinc proceed 
as follows : Boil for several hours commercial zinc-gray, i. e., 
very finely-divided metallic zinc, with concentrated solution 
of caustic soda. Then immerse the articles to be zincked in 
the boiling fluid, when, by continued boiling, they will in a 
short time become coated with a very bright layer of zinc. 
When a copper article thus coated with zinc is carefully 
heated in an oil bath to between 248 and 284 F., the zinc 
alloys with the copper, forming a sort of bronze similar to 
tombac. 



39^ ELECTRO- DEPOSITION OF METALS. 

Weil zincks copper and coppered objects by immersing therri 
in a boiling concentrated solution of caustic potash in contact 
with zinc. The coating thus obtained is said to be adherent 
and brilliant. 

For coloring and patinizing zinc, see special chapter. 

Zinc alloys. — The production of the principal zinc alloy, 
brass, by the galvanic method, having already been mentioned, 
and also that of a zinc-nickel -copper alloy (German silver), it 
remains to give an alloy of zinc with tin, or of zinc, tin and 
nickel, which can be produced by the use of the battery. 

A suitable bath for depositing this alloy consists of: Chlo- 
ride of zinc 6^ drachms, crystallized stannous chloride 9 
drachms, pulverized tartar 9 drachms, pyrophosphate of soda 
2^ drachms, water 1 quart. Dissolve the salt at a boiling 
heat, and filter the cold solution, when it is ready for use. For 
anodes, cast plates of equal parts of tin and zinc are used. 

These deposits have no special advantages, but, ort the other 
hand, a deposit containing zinc in large excess has the same 
effect of protecting iron from rust as a deposit of pure zinc. 

By preparing a bath which contains as conducting salt sodium 
citrate, and ammonium chloride and the chlorides of the metals 
in the proportion of 4 zinc chloride to 1 tin chloride, a deposit 
is obtained, which not only is a perfect protection against rust, 
but also enters far better into depressions than pure zinc; By 
adding to the bath a small quantity of chloride of mercury, or 
of nickel, alloys of zinc, tin and mercury, or of zinc, tin and 
nickel are formed, which are distinguished from pure zinc de- 
posits by a finer structure. 

3. Deposition of Lead. 
The properties of lead only interest us in so far as it is less 
attacked by most mineral acids than any other metals, and ob- 
jects have been coated with it, in order to protect them against 
the action of such agents. For decorative purposes electro- 
deposits of lead are not used, and those as a protection against 
chemical influences cannot be produced of sufficient thickness 
for that purpose. 



DEPOSITION OF TIN, ZINC, LEAD, AND IRON. 397 

Lead baths. — I. Dissolve, by continued boiling, caustic pot- 
ash 1.75 ozs. and finely pulverized litharge 0.17 oz. in 1 quart 
of water. 

II. According to Watt, the following solution is used : Ace- 
tate of lead 0.17 oz., acetic acid 0.17 oz., water 1 quart. 

The bath prepared according to formula I. deserves the 
preference. 

Lead baths require anodes of sheet-lead or cast-lead plates, 
a very weak current, and in order to produce a dense deposit 
of some thickness, the objects have to be frequently scratch- 
brushed. Iron is best previously coppered. Superoxide of 
lead being separated from the anodes, they have to be fre- 
quently cleansed with a scratch-brush. The formation of 
superoxide of lead is utilized for the production of the so- 
called Nobili's rings (electrochromy), which will be mentioned 
below. 

To coat gun barrels and other articles of steel or iron with 
superoxide of lead as a protection against rust, suspend the 
bright articles as anodes in a solution of nitrate of lead mixed 
with ammonium nitrate. 

Leading by contact is effected by suspending the objects, 
previously thoroughly freed from grease, in the boiling solution 
prepared according to formula I., in contact with a piece of tin. 

Metallo-chromes (Nobili's rings, iridescent colors, electro- 
chromy). The separation of superoxide of lead upon the 
anodes or upon objects suspended as anodes, produces superb 
effects of colors. For the production of such colors, a bath is 
prepared by boiling for half an hour 3^ ozs. of caustic potash, 
14 drachms of litharge, and 1 quart of water. The operation 
is as follows : Suspend the articles, carefully freed from grease 
and pickled, to the anode-rods, and with a weak current intro- 
duce in the lead solution a thin platinum wire connected with 
the object-rod by flexible copper wire, without, however, touch- 
ing the article. The latter will successively become colored 
with various shades — yellow, green, red, violet, and blue. By 
the continued action of the current, these colors pass into a 



398 ELECTRO-DEPOSITION OF METALS. 

discolored brown, which also appears in the beginning if the 
current be too strong, or the platinum wire be immersed too 
deep. Such unsuccessful coloration has to be removed by 
rapidly dipping in nitric acid, and, after rinsing in water, sus- 
pending the article in the bath. For coloring not too large 
surfaces, a medium-sized Bunsen element is, as a rule, sufficient, 
if the platinum wire be immersed about ^ inch. 

Colors of all possible beautiful contrasts may be obtained by 
perpendicularly placing between the objects to be colored and 
the platinum wire a piece of stout parchment paper, or pro- 
viding the latter with many holes or radial segments. 

Another process of producing these effects of colors is as 
follows : Prepare a concentrated solution of acetate of lead 
{sugar of lead), and after being filtered, pour it into a shallow 
porcelain dish. Then immerse a plate of polished steel in the 
solution, and allow it to rest upon the bottom of the dish. 
Now connect a small disc of sheet copper with the wire proceed- 
ing from the zinc element of a constant battery of two or three 
cells, the wire connected with the copper element being placed 
in contact with the steel plate. If now the copper disc be 
brought as close to the steel plate as possible without touching 
it, in a few moments a series of beautiful prismatic colorations 
will appear upon the steel surface, when the plate should be 
removed and rinsed in clean water. These colorations are 
films of lead in the form of peroxide, and the varied hues are 
due to the difference in thickness of the precipitated peroxide 
of lead, the light being reflected through them from the pol- 
ished metallic surface beneath. By reflected light every pris- 
matic color is visible, and by transmitted light a series of pris- 
matic colors complementary to the first colors will appear 
occupying the place of the former series. The colors are seen 
to the greatest perfection by placing the plate before a window 
with the back to the light, and holding a piece of white paper 
at such an angle as to be reflected upon its surface. The 
colorations are not of a fugitive character, but will bear a con- 
siderable amount of friction without being removed. In proof 



DEPOSITION OF TIN, ZINC, LEAD, AND IRON. 399 

of the lead oxide being deposited in films or layers, it may be 
stated that if the deposit be allowed to proceed a few seconds 
beyond the time when its greatest beauties are exhibited, the 
coloration will be less marked, and become more or less red, 
green or brown. If well rubbed, when dry, with the finger or 
fleshy part of the hand, a rich blue colored film will be laid 
bare by the removal of the delicate film above it. 

The plan recommended by Mr. Gassiot to obtain the metallo- 
chromes is to place over the steel plate a piece of card cut 
into some regular device, and over this a rim of wood, the 
copper disc being placed above this. Very beautiful effects 
are obtained when a piece of fine copper wire is turned up in 
the form of a ring, star, cross or other pattern, and connected 
with the positive electrode, this being in fact one of the simplest 
and readiest methods of obtaining the colorations upon the 
polished metal. Metallo-chromy is extensively employed in 
Nuremberg to ornament metallic toys. It has been adopted 
in France for coloring bells, and in Switzerland for coloring 
the hands and dials of watches. In using the lead solutions to 
produce metallo-chromes, it must be remembered that me- 
tallic lead becomes deposited upon the cathode, consequently 
the solutions in time become exhausted, and must therefore be 
renewed by the addition of the lead salt. 

4. Deposition of Iron (Steeling). 

The principal practical use of the electro-deposition of iron 
is to coat printing plates of softer metal to increase their wear- 
ing qualities. We are indebted to B'5ttger for calling attention 
to the employment of iron deposits, but notwithstanding the 
efforts of many scientific and practical men to improve the 
process, the expectation entirely to replace copper galvano • 
plasty for cliches by iron-galvanoplasty has not been fulfilled. 

Only such baths as are suitable for steeling will here be 
given. Solutions for the production of thick iron deposits, and 
the conditions under which they can be obtained, will be re- 
ferred to later on under " Galvanoplasty in Steel." 



400 ELECTRO-DEPOSITION OF METALS. 

Iron ■ steel) baths. — I. According to Varrentrapp : Pure 
green vitriol 4^ ozs., sal ammoniac 3^ ozs., water 1 quart. 
Boil the water for ]/ 2 hour to expel all air, and, after cooling, 
add the green vitriol and sal ammoniac. By the action of the 
air, and the oxygen appearing on the anodes, this bath is 
readily decomposed, insoluble basic sulphate of iron being 
separated as a delicate powder, which has to be frequently re- 
moved from the fluid by filtering. To decrease decomposition, 
the double sulphate of iron and ammonium, which can be more 
readily obtained pure and free from oxide, may be used. 

II. Sal ammoniac ^y 2 ozs., water 1 quart. This neutral 
solution of sal ammoniac may be made into an iron bath by 
hanging in it iron sheets as anodes, suspending an iron or cop- 
per plate as cathode, and allowing the current to circulate until 
a regular separation of iron is attained, which is generally the 
case in 5 to 6 hours. Although a separation of hydrated oxide 
of iron also takes place in this bath, it does so in a less degree 
than in that prepared according to Formula I. For the pro- 
duction of not too heavy a deposit of iron, some operators 
claim to have obtained the best results with this bath. 

According to Bottger, the following bath serves for steeling: 

III. Potassium ferrocyanide (yellow prussiate of potash) 
0.35 oz., Rochelle salt 0.7 oz., distilled water 200 cubic centi- 
meters. To this solution is added a solution of 1.69 drachms 
of persulphate of iron in 50 cubic centimeters of water, whereby 
a moderate separation of Berlin blue takes place. Then add, 
drop by drop, whilst stirring constantly, solution of caustic 
soda until the blue precipitate has disappeared. The clear, 
slightly yellowish solution thus obtained can be used directly 
for steeling. 

A heavy and very hard deposit of iron is obtained in a bath 
of the following composition : 

IV. Ammonio-ferrous sulphate 1% ozs., crystallized citric 
acid 0.88 oz., water 1 quart; sufficient ammonia for alkaline 
reaction. 

For steeling his copper printing plates, which are frequently 



DEPOSITION OF TIN, ZINC, LEAD, AND IRON. 4OI 

of quite large dimensions, C. Obernetter, of Munich, employs 
the following method : The plate to be steeled is first freed 
from all color, which is best effected by means of chloroform 
or oil of turpentine. It is then thoroughly washed and brushed 
by means of a bristle-brush with potash lye, or a solution of 1 
part potassium cyanide in 20 parts water, and again washed. 
In this state the plate is suspended to the cathode of the steel- 
ing bath. A clean steel plate serves as anode. Both the 
anode and cathode are in a horizontal position. Bubbles form- 
ing on the cathode are readily removed by means of a feather. 
In about five minutes the plate is thoroughly steeled. 

The iron bath consists, according to Obernetter, of ferrous 
sulphate 30 parts by weight, iron- alum 30, sal ammoniac 60, 
dissolved in warm distilled water 1000. 

The solution is allowed to stand for two days, and is then 
filtered twice. It should also be filtered every time before use. 

After steeling, the plate is cleansed in the above-described 
manner, and oiled to prevent rusting. 

When, during the operation of printing, the deep places of 
the plate commence to become red, i. e., when the copper 
shines through, the steeled plate may be re-steeled, but, ac- 
cording to Obernetter, this should not be done more than 
once. It is best in every case to first remove the old steeling 
with dilute sulphuric or nitric acid, and then to re-steel the 
plate. 

According to Obernetter's statements, 21,000 copies were 
printed from a plate thus steeled without the plate suffering 
any injury, the last impressicn being in every respect equal to 
the first. 

For decorative purposes, a deep black deposit of iron may, 
according to " La Metallurgie," be produced as follows : Dis- 
solve as large a quantity of steel filings as possible in 50 quarts 
of commercial hydrochloric acid. The saturation of the solu- 
tion is recognized by a sediment, which no longer dissolves, 
being formed on the bottom of the vessel. Then add 2 lbs. 
of white arsenic, and vigorously stir the mixture. The arsenic 
26 



402 ELECTRO-DEPOSITION OF METALS. 

dissolves very slowly, but the bath cannot be considered 
finished until all of it is dissolved, and the color obtained by 
means of the bath is the deeper the more complete the solution 
of the arsenic. The articles to be treated are connected to the 
negative pole of the battery, iron and carbon plates serving 
as anodes. For a bath of 50 quarts, two Bunsen elements 
about 7^ inches high are required, and the bath being very 
acid, the articles must be connected with the battery prior to 
immersion. Upon copper and brass the deposit is directly 
produced, but iron articles, being attacked by the bath, are first 
provided with a coat of nickel. The deposit of iron upon this 
nickel, coating is very beautiful, and has been designated as 
" black nickeling." The coating must, of course, be protected 
from oxidation by a colorless lacquer. 

Management of iron baths. — As previously mentioned, the 
insoluble precipitate from time to time formed in the bath has 
to be removed by filtration. This precipitate is, however, 
very delicate, and when stirred up might settle upon the objects 
and prevent the adherence of the deposit. It is, therefore, 
advisable to use for steel baths, tanks of much greater depth 
than corresponds to the height of the objects, whereby the 
stirring up of the sediment in suspending the objects is best 
avoided. The baths must be kept thoroughly neutral, which 
may be effected in various ways. One method is to suspend 
small linen bags filled with carbonate of magnesia in the bath. 
Another method, which has been used with decided success, 
consists in precipitating, whilst excluding the air as much as 
possible, a solution of pure green vitriol with ammonium car- 
bonate, quickly filtering off the ferrous carbonate, washing the 
latter once or twice in cold water previously boiled, stirring it 
while moist into the bath, and allowing to repose for one hour. 

The cleansed and pickled objects are plated in the baths 
according to formulae I. and II., with a current of 1.5 to 2 
volts, and the anodes at a distance of 4 to 4 }( inches, after 
which the current is reduced to 1 or 1.25 volts. To produce 
iron deposits of any kind of thickness, the escape of the hy- 



DEPOSITION OF TIN, ZINC, LEAD, AND IRON. 403 

drogen bubbles which settle on the objects must be promoted 
by frequent blows with the finger upon the object-rod. As 
anodes, iron sheets of a large surface freed from scale by pick- 
ling are to be used. When steeling is finished, the articles are 
thoroughly rinsed, then plunged into very hot water, and, after 
drying in sawdust, placed for several hours in a drying cham- 
ber heated to about 21 2° F., to expel all moisture from the 
pores. 

Steeling of printing plates has the advantage over nickeling, 
that when the plates are worn they can be rapidly freed from 
the deposit by dilute sulphuric acid or very dilute nitric acid, 
and re-steeled. It has been ascertained by experiments that 
the capability of resistance of steeled plates is less than that of 
nickeled plates, 200,000 impressions having been made with 
the latter without any perceptible wear. 

For steeling printing plates a bath prepared according to for- 
mula I. or II. is very suitable. 

Steeling by contact is readily effected by touching the metallic 
objects with zinc, best in a bath prepared according to for- 
mula I. 



CHAPTER XIII. 

DEPOSITION OF ANTIMONY, ARSENIC, ALUMINIUM. 

i. Deposition of Antimony. 

Properties of antimony. — Electro-deposited antimony pos- 
sesses a gray lustre, while native, fused antimony shows a silver- 
white color. Antimony is hard, very brittle, and may easily be 
reduced to powder in a mortar. It melts at 842 F., and at a 
strong red heat takes fire and burns with a white flame, form- 
ing the trioxide. Its specific gravity is 6.S. It is permanent 
in the air at ordinary temperatures. Cold, dilute or concen- 
trated sulphuric acid has no effect upon antimony, but the 
hot concentrated acid forms sulphide of antimony. By nitric 
acid the metal is more or less energetically oxidized, according 
to the strength and temperature of the acid. 

Antimony baths. — Electro-depositions of antimony are but 
seldom made use of in the industries, though they are very 
suitable for the production of contrasts in decorating. Gore 
discovered the explosive power of deposits of antimony chloride 
or of antimony containing hydrochloric acid. According to 
Gore, a bath consisting of tartar emetic 3 ozs., hydrochloric acid 
41^ ozs., tartaric acid 3 ozs. and water 1 quart, yields a gray 
crystalline deposit of antimony. This bath requires a current 
of about three volts. The deposit possesses the property of 
exploding when scratched with a hard object. This explosion 
is caused by a content of chloride of antimony. Bottger found 
3 to 5 per cent, of chloride of antimony in the deposit, and Gore 
6 per cent. A similar explosive deposit is obtained by electro- 
lyzing a simple solution of chloride of antimony in hydrochloric 
acid (liquid butter of antimony, liquor stibii chlorati) with the 
current. 

( 404 ) 



DEPOSITION OF ANTIMONY, ARSENIC, ALUMINIUM. 405 

A lustrous non-explosive deposit of antimony is obtained by 
boiling 4.4 ozs. of carbonate of potash, 2. 11 ozs. of pulverized 
antimony sulphide, and I quart of water for I hour, replacing 
the water lost by evaporation, and filtering. Use the bath 
boiling hot, employing cast antimony plates or platinum sheets 
as anodes. 

An antimony bath which yields good results is composed as 
follows : 

Schlippe's salt I ^ ozs., water 1 liter. Dissolve the salt in 
the water. Tension required, 4 volts. An unpleasant feature 
of this bath is that during electrolyzing sulphuretted hydrogen 
escapes, which limits its application. 

Schlippe's salt, named after its discoverer, is easily formed 
by boiling an aqueous solution of sodium sulphide with anti- 
mony trisulphide and sufficient sulphur to convert it into the 
pentasulphide. Instead of sodium sulphide, caustic soda and 
sulphur may be used, which on boiling yield sodium sulphide 
and sodium thiosulphate ; or, instead of caustic soda, sodium 
carbonate and slaked lime. To prepare the compound, 9 parts 
of crystallized sodium carbonate are boiled with 3 parts of 
slaked lime, 3 parts of antimony trisulphide, 1 part of sulphur, 
and sufficient water. The hot liquid is rapidly filtered off from 
the calcium carbonate and evaporated down until the salt crys- 
tallizes out. The crystals so obtained must be preserved in 
well-stoppered bottles, as the carbonic anhydride of the air 
decomposes them, forming sodium carbonate, sulphuretted 
hydrogen and antimony sulphide. This causes the colorless, 
or, at most, pale yellow crystals to become gradually covered 
with an amorphous brown- colored crust. 

2. Deposition of Arsenic. 
Properties of arsenic. — Arsenic has a gray- white color, a 
strong metallic lustre, is very brittle, and evaporates at a red 
heat. In dry air arsenic retains its lustre, but soon turns dark 
in moist air. It is scarcely attacked by dilute hydrochloric 
and sulphuric acids, while concentrated sulphuric acid as well 



406 ELECTRO-DEPOSITION OF METALS. 

as nitric acid oxidizes it to arsenious acid. If caustic alkalies 
are fused together with arsenic, a portion of the latter is con- 
verted into alkaline arsenate. 

Arsenic baths. — Deposits of arsenic are more frequently used 
than antimony deposits for decorative purposes, in order to 
produce a blue-gray tone of a certain warmth, which is very 
effective in combination with bright copper, brass, etc. 

A solution suitable for depositing arsenic upon all kinds of 
metals is as follows : 

I. Pulverized arsenious acid I ^ ozs., crystallized pyrophos- 
phate of soda 0.7 oz., 98 per cent, potassium cyanide \y± ozs., 
water I quart. 

Dissolve the pyrophosphate of soda and the potassium 
cyanide in the cold water, and after adding, whilst stirring, the 
arsenious acid, heat until the latter is dissolved. In heating, 
fumes containing prussic acid escape, the inhalation of which 
must be carefully avoided. The bath is used warm, and requires 
a vigorous current of at least 4 volts, so that, at the least, 3 
Bunsen elements have to be coupled for tension. After sus- 
pending the objects they are first colored black-blue, the color 
passing with the increasing thickness of the deposit into pale 
blue, and finally into the true arsenic gray. Platinum sheets 
or carbon plates are to be used as anodes. 

Instead of a bath prepared according to formula I., a solu- 
tion of the following composition may be used: 

II. Sodium arsenate 1 ^ ozs., 98 per cent, potassium cyanide 
0.8 oz., water 1 quart. Boil the solution for half an hour, then 
filter and use it at a temperature of at least 167 to 176 F., 
with a strong current. It yields a good deposit. 

Large baths, to be used cold, must be more concentrated, 
and require a stronger current than hot baths. 

When the baths begin to work irregularly and sluggishly, 
they have to be replaced by fresh solutions. 

In the execution of deposits of arsenic and antimony the 
same rules are to be observed as for the other electro-plating 
processes. 



DEPOSITION OF ANTIMONY, ARSENIC, ALUMINIUM. 407 

However, attention may here be called to one phenomenon 
which is frequently the cause of defective deposits. When, for 
instance, mountings of zinc, such as are used for book covers, 
jewel boxes, etc., are to be provided with a deposit of copper 
and arsenic, and hence are to show two colors, it is necessary 
to first copper them. After polishing and cleaning the cop- 
pered mountings, the places which are not to receive the blue- 
gray deposit of arsenic are coated with stopping-off varnish. 
When articles thus treated, after being again freed from grease 
and pickled, are brought into the arsenic bath, they frequently 
show ugly stains the size of a pin-head. This phenomenon, 
however, does not appear when the articles before being 
brought into the bath are drawn through water acidulated with 
a small quantity of nitric acid (about J^ oz. of nitric acid to 1 
quart of water), and thoroughly rinsed in clean water. 

Deposits of antimony and arsenic by contact and immersion 
are much used for coloring brass and copper, as well as iron 
(browning of gun-barrels), and silver. Most frequently a warm 
solution of antimony trichloride (the butter of antimony of 
commerce) in hydrochloric acid is used for this purpose, in 
which the clean and pickled brass articles acquire a coating of 
a steel-gray color with a bluish tinge. By using instead, a hot 
mixture of chloride of arsenic with a small quantity of water, a 
steel-gray color without a bluish tinge is obtained. 

By immersing brass in a solution of 20 parts by weight of 
arsenious acid, 40 of hydrochloric acid, 800 of water, and 10 of 
sulphuric acid heated to between 122 and 140 F., it becomes 
black by the separation of pulverulent arsenic ; after rinsing in 
water and drying the coat adheres quite well. By contact with 
zinc the deposit is obtained in a shorter time and adheres 
better. 

3. Deposition of Aluminium. 

Properties of aluminium. — Aluminium is a white silvery metal 
with an almost imperceptible bluish tinge. It is extremely 
light, the specific gravity being only 2.58, is very malleable and 



408 ELECTRO-DEPOSITION OF METALS. 

ductile, takes a high polish, and is not liable to tarnish in the 
air. It melts at about 1300 F. Its principal common impur- 
ities are iron and silicon. 

Aluminium does not seem to possess any qualities which 
would make it advantageous as an electro -deposit upon other 
metals. Many solutions have been proposed which it was 
claimed should give good deposits of the metal, but, on trial, 
have been found to be worthless. The solutions given below 
are claimed to give good results, but are here mentioned with 
due reserve. 

Alumi7iium baths. — I. Bertrand states that he has deposited 
aluminium upon a plate of copper in a solution of the double 
chloride of aluminium and ammonium by using a strong current 
from three Bunsen elements, the bath being worked at 140 F. 

II. Goze's process. — Mr. Goze obtained a deposit of alumin- 
ium by the single-cell method from a dilute solution of the 
chloride. The liquid was placed in a jar in which was im- 
mersed a porous cell containing dilute sulphuric acid ; an 
amalgamated zinc plate was immersed in the acid solution, and 
a plate of copper in the chloride solution, the two metals being 
connected by a copper conducting wire. At the end of some 
hours the copper plate became coated with a lead-colored de- 
posit of aluminium, which when burnished, presented the 
same degree of whiteness as platinum, and did not appear to 
tarnish readily when immersed in cold water, or exposed to the 
atmosphere, but was acted upon by dilute sulphuric and nitric 
acids. 

III. The following formula is given by Mr. Herman Rein- 
bold, who states that it yields excellent results: Dissolve 50 
parts by weight of alum in 300 of water, and to this add 10 
parts of aluminium chloride. The solution is to be heated to 
200° F., and, when cold, 39 parts of potassium cyanide are to 
be added. A feeble current should be used. 

IV. A new method for the electro-deposition of aluminium 
is as follows: * To a 20 per cent, solution of ammonium-alum 

* Neueste Erfindungen und Erfahrungen, vol. xix., p. 353. 



DEPOSITION OF ANTIMONY, ARSENIC, ALUMINIUM. 409 

in warm water, add a solution of about the same quantity of 
pearl-ash and of a small quantity of ammonium carbonate. 
The mixture effervesces and yields a precipitate, which is fil- 
tered off and thoroughly washed with water. Over the pre- 
cipitate thus obtained pour a warm solution of 16 per cent, 
ammonium-alum and 8 per cent, pure potassium cyanide, and 
boil the whole in a closed iron vessel for 30 minutes. The 
proper proportions for the solutions are as follows : First alum 
solution: Ammonium-alum 4 lbs., water 10 quarts. Pearl-ask 
solution: Pearl-ash 4 lbs., warm water 10 quarts, ammonium 
carbonate 4^ to 5^ drachms. Second alum solution: Am- 
monium-alum 8 lbs., warm water 25 quarts, potassium cyanide 
4 lbs., then add 20 quarts of water and about 4 lbs. more of 
potassium cyanide, and let the whole boil for about J^ hour. 
The filtered solution is then ready for use as the electrolytic 
bath. As anodes perforated aluminium plates are used, which 
can be raised and lowered. The cathodes receive the deposit. 
The bath is maintained at a temperature of between 8o° and 
149 F. By adding pieces of other metals, such as gold, 
silver, nickel, copper, etc., to the aluminium anodes, the color 
of the deposit may be somewhat changed. If the deposit 
shows a gray coloration it is made lustrous by dipping in a 
solution of caustic soda, which also prevents oxidation. 

Electro-depositions upon aluminium. — The electro-deposition 
of other metals upon aluminium presents many difficulties 
which are chiefly due to the behavior of this metal in the plat- 
ing baths. The deposits to be sure are formed, but they pos- 
sess no adherence, and especially baths containing potassium 
cyanide yield the worst results in consequence of the effect of 
alkaline solutions upon the basis-metal Since the production 
of aluminium has so largely increased, and a great number of 
articles of luxury and for practical use are now made of this 
metal, the need of decorating such articles by electro -plating 
or covering them entirely with other metals has been felt, 
since the color of aluminium is by no means a sympathetic one. 
Look into a show window where aluminium articles are 



41 ELECTRO-DEPOSITION OF METALS. 

exposed — nothing but gray in gray. Offended, the eye of 
the observer turns away, and seeks a more agreeable resting 
place. 

Aluminium behaves so differently from other metals towards 
the cleansing agents usually used that different methods from 
those previously described have to be employed in preparing 
it for plating. Nitric acid has almost no effect on aluminium, 
and pickle just as little; but, on the other hand, the metal is 
attacked by concentrated hydrochloric acid, dilute hydro- 
fluoric acid, and especially by alkaline lyes. Hence if polished 
articles of aluminium are to be prepared for plating, alkaline 
lyes will have to be avoided in freeing them from grease, it 
being best to use only benzine for the purpose. Unpolished 
articles may without hesitation be freed from grease with caus- 
tic potash or soda lye, and for the production of a dead white 
surface be for a short time pickled in dilute hydrofluoric acid, 
and then thoroughly rinsed in running water. For producing 
an electro-deposit upon aluminium it has been considered ad- 
visable to first copper the metal, and the Aluminium Gesell- 
schaft of Neuhausen recommends for this purpose a solution of 
nitrate of copper. But the adherence of the copper proved 
also insufficient, because in the subsequent silvering, nickeling, 
etc., the deposit raised up. 

The copper bath recommended by Delval, consisting of 
sodium pyrophosphate 3 ozs., copper sulphate (copper 
vitriol) ^ oz., sodium bisulphite ^ oz., water 1 quart, also 
proved unreliable. 

According to another patented process, plating of aluminium 
is claimed to be effected successfully, and without defect, by 
lightly coating the metal with silver amalgam by boiling in a 
silver bath compounded with potassium mercury cyanide. 
However, this treatment did not always yield reliable results. 

According to Villon, articles of aluminium are to be im- 
mersed for one hour in a bath consisting of glycerin 5^ ozs., 
zinc cyanide 0.88 oz., zinc iodide 0.88 oz., and then heated to 
a red heat. When cold, they are washed with a hard brush 



DEPOSITION OF ANTIMONY, ARSENIC, ALUMINIUM. 41 I 

and water, and brought into the gold or silver bath. The suc- 
cess of this process seems also questionable. 

The best and most reliable process is without doubt the one 
patented, in i8<j3, by Prof. Nees. It consists in first immersing 
the aluminium articles previously freed from grease in caustic 
soda lye until the action of the lye upon the metal is recognized 
by gas bubbles rising to the surface. The articles without 
being previously rinsed are then for a few minutes immersed in 
a solution of JJ troy grains of chloride of mercury, rinsed, 
again brought into the caustic soda lye, and then, without 
rinsing, suspended in the silver bath. The deposit of silver 
thus obtained adheres very firmly, and can be scratch-brushed 
and polished with the steel without raising up. It can also be 
directly gilded, brassed, or, after previous coppering in the 
potassium cyanide copper bath, provided with a heavy deposit 
of nickel and polished upon polishing wheels. 

The Mannesmann Pipe Works, Germany, produce durable 
electro-deposits by brushing the aluminium with solutions of 
sulphide of gold and sulphide of silver in balsam of sulphur * 
and volatile oils, and burning in the metals in a muffle, under 
exclusion of the air, at 840 to 930 F. Thin layers of metal 
which are separated adhere firmly to the aluminium, and are 
then provided with any electro-deposit desired. According to 
a process patented by the same corporation the articles are 
provided with a firmly adhering( ?) film of zinc by immersing 
them in boiling solution of zinc dust in caustic soda, and are 
then electro-plated. 

* Solution of sulphur in linseed oil. 



CHAPTER XIV. 

GALVANOPLASTY (REPRODUCTION). 

By galvanoplasty proper is understood the production, with 
the assistance of the electric current, of copies of articles of 
various kinds, true to nature, and of sufficient thickness to form 
a resisting body, which may be detached from the object ser- 
ving as a mould. 

Copper is the most suitable metal for galvanoplastic pro- 
cesses, that which is precipitated by electrolysis showing the 
following valuable properties. It may be precipitated chemi- 
cally pure, and in this state is less subject to change than ordi- 
nary commercial copper, or the copper alloys in general use, 
its tensile strength being 20 per cent, greater than that of 
smelted copper. Its hardness is also greater, while its specific 
gravity (18.85) nes between that of cast and rolled copper. 

The physical properties of copper deposited by electrolysis 
are dependent on the condition of the bath, as well as on the 
intensity and tension of the current. 

The bath used for depositing copper is in all cases a solution 
of blue vitriol. Smee proved by experiments that, with as in- 
tense a current strength as possible without the evolution of 
hydrogen, the copper is obtained as a tenacious, fine-grained 
deposit. But when the current-strength is so intense that hy- 
drogen is liberated, copper in a sandy, pulverulent form is ob- 
tained, and in a coarsely crystalline form when the current- 
strength is very slight. 

At a more recent period, Hiibl instituted a series of sys- 
tematic experiments for the determination of the conditions 
under which deposits with different physical properties are 
obtained. Hiibl worked with 5 per cent, neutral, and 5 per 

(412) 



GALVANOPLASTY (REPRODUCTION). , 413 

cent, acid, solutions of copper, as well as with 20 per cent, 
neutral, and 20 per cent, acid, solutions. The neutral solutions 
were prepared by boiling blue vitriol solution with carbonate of 
copper in excess, and the acid solutions by adding 2 per cent, 
of sulphuric acid of 66° Be. The result was that in the neutral 
5 per cent, solutions less brittle deposits were obtained with a 
slight current-density than in a more concentrated solution, 
though the appearance of the deposits was the same. The ex- 
periments with acidulated baths confirmed the fact that free 
sulphuric acid promotes the formation of very fine-grained de- 
posits even with very slight current-densities, and it would seem 
that the brittleness of copper deposited from acid baths is in- 
fluenced less by the concentration than by the current-density 
used. 

The process used in galvanoplasty may be arranged in two 
classes, viz., the deposition of copper with, or without, the use of 
external sources of current, the first comprising galvanoplastic 
deposits produced by means of the single-cell apparatus, and 
the other those by the battery, thermo-electric pile, dynamo 
or accumulator. 

1 . Galvanoplastic Deposition in the Cell Apparatus. 

The cell apparatus consists of a vessel containing blue vitriol 
solution kept saturated by a few crystals of blue vitriol placed 
in a muslin bag or a small perforated box of wood, stoneware, 
etc. In this vessel are placed round or square porous clay 
cells (diaphragms) which contain dilute sulphuric acid and a 
zinc plate, the zinc plates being connected with each other 
and with the objects to be moulded — which may be cither 
metallic or made conductive by graphite — by copper wire or 
copper rods. The objects to be moulded play the same role 
as the copper electrode in a Daniell element, and the cell ap- 
paratus is but a species of Daniell element in which the in- 
ternal, instead of the external, current is utilized. 

As soon as the circuit is closed by the contact of the objects 
to be moulded with the zinc of the porous cell, the electrolytic 



414 



ELECTRO-DEPOSITION OF METALS. 



Fig. 140. 



process begins. The zinc is oxidized by the oxygen, and with 
the sulphuric acid forms zinc sulphate (white vitriol), while the 
copper is reduced from the blue vitriol solution and deposited 
in a homogeneous layer upon the articles to be moulded. 

A simple apparatus frequently used by amateurs for mould- 
ing metals, reliefs, etc., is shown in Fig. 140. 

In a cylindrical vessel of glass or stoneware filled with satu- 
rated blue vitriol solution is placed a porous clay cell, and in 
the latter a zinc cylinder projecting about 0.039 to 0.079 inch 

above the porous clay cell. To 
the zinc is soldered a copper 
ring, as plainly shown in the 
illustration. The clay cell is 
filled with dilute sulphuric acid 
( 1 acid to 30 water), to which 
some amalgamating salt may be 
suitably added. The articles to 
be moulded are suspended to 
the copper ring, care being had 
to have the surfaces which are 
to be covered near and opposite 
to the cell. To supplement the 
content of copper, small linen 
or sail-cloth bags filled with blue 
vitriol are attached to the upper edge of the vessel. 

Fig. 141 shows another form of cell-apparatus which is much 
used in printing establishments for the production of cliches. 
A is a large box lined with gutta-percha. In this box is sus- 
pended a smaller box, B, the bottom of which is formed of a 
disk of leather or parchment. To the side of this box are 
nailed strips, b. To these strips is secured a piece of stout 
linen, which serves partially as a support of the zinc plate, Zn, 
and partially to prevent impurities of the zinc from falling upon 
the leather disk. The zinc plate is connected with the strap, 
K, which is made of thin sheet copper. In the box, A, lies the 
board, D, which is sufficiently weighted with strips of lead to 




GALVANOPLASTY (REPRODUCTION) 



415 



prevent it from floating in the fluid. To prevent the separa- 
tion of copper, these lead strips are coated with a varnish made 
from sealing-wax or with gutta-percha. To the upper side of the 
board is nailed the copper strap, K' ', which is insulated as far 
as it touches the fluid and the board by a coating of gutta- 
percha. The binding screw, E, connects the two copper straps. 
A perforated copper sheet bent in the form of a gutter dips 
above in the copper solution. During the operation this coppei 
sheet is kept filled with crystals of blue vitriol, and serves to 
maintain a uniform saturation of the fluid. 

To produce deposits with this apparatus, the first matrice is 
laid upon the portion of copper strap upon the board, D. The 
copper strap is then connected with the conducting surface by 

Fig. 141. 




driving a brass pin through the matrice and the strap into the 
board. Underneath the other end of the matrice is placed a 
small piece of copper sheet insulated by gutta-percha, so that 
it projects y? to y± inch beneath the matrice. It is also 
brought in contact with the conducting surface by means of a 
brass pin. Upon this sheet is placed the second matrice, 
which is also secured with a brass pin, and so on, until all the 
moulds upon which the copper is to be deposited are upon the 
board. The surfaces of the moulds, as well as the heads of 
the pins, are then carefully rubbed with graphite, and the 
board is brought into the box filled with the vitriol solution. 
The box, B, with the zinc plate is then suspended in the box, 



4 i6 



ELECTRO-DEPOSITION OF METALS. 



A, and after filling it with dilute sulphuric acid, the two copper 
straps are connected by the binding screw, E. The electric 
current then passes through the latter, and the pin to the sur- 
face of the first matrice, and after depositing copper upon it 
passes through the second pin and the small copper plate to 
the second matrice, and so on, effecting a uniform deposit of 
copper upon all conducting surfaces connected with each other. 
Large apparatus.— To cover large surfaces, large, square 
tanks of stoneware, or wood, lined with lead, gutta percha, or 



Fig. 142. 




another substance unacted upon by the bath are used. For 
baths up to three feet long, stoneware vats are to be preferred. 
Fig. 142 shows the French form of cell apparatus. In the 
middle of the vat, and in the direction of its length, is disposed 
a row of cylindrical cells, close to each other, each provided 
with its zinc cylinder. A thin metallic ribbon is connected 
with ail the binding screws of the cylinder, and is in contact at 
its extremities with two metallic bands on the ledges of the 
depositing vat. The metallic rods supporting the moulds are 






GALVANOPLASTY (REPRODUCTION). 



417 



in contact with the metallic bands of the ledges, and, therefore, 
in connection with the zincs. 

The German form of cell apparatus is shown in Fig. 143. 
It is provided with long, narrow, rectangular cells of a corre- 
spondingly greater height than the column of fluid. 

Across the vat are placed three conducting rods connected 
with each other by binding screws and copper wire. To the 
centre rod, which lies over the cells, are suspended the zinc 
plates by means of a hook, while the two outer rods serve for 
the reception of the moulds. 

The size of the zinc surfaces in the simple apparatus should 

Fig. 143. 




be about equal to that of the surfaces to be moulded, if dilute 
sulphuric acid (1 acid to 30 water) is to be used. For par- 
ticulars see " Execution of the Galvanoplastic Deposition of 
Copper." 

The copper bath for the cell apparatus consists best of 3 
moderately saturated solution of pure blue vitriol, free from 
iron, in water free from lime, and should show abont 18 to 20 
Be., a bath of 100 quarts requiring about 20 to 24 lbs. of blue 
vitriol. The following table gives the approximate content of 
pure crystallized blue vitriol at different degrees Be., and at 
59° F. 

27 



4i8 



ELECTRO-DEPOSITION OF METALS. 



Degrees, Be. 



5° 
io° 

12° 

1 6° 
i 7 ° 
1 8° 
i 9 G 

20 c 

21° 
22° 




This solution contains 
crystallized blue vitriol. 



5 per cent. 
ii " 

13 " 

17 " 

18 

19 " 

20 " 
21 

23 
24 
25 « 



While to a copper bath working with the use of an external 
source of current, more or less sulphuric acid is added, accord- 
ing to requirements, baths in the single cell apparatus do not 
require such addition, because a considerable quantity of the 
acid in the clay cell gradually penetrates by osmose into the 
bath, and not only of the acid alone, but also of the white 
vitriol solution formed, whereby the working duration of the 
bath is considerably reduced. Furthermore, the sulphuric 
acid liberated by the separation of copper from the blue vitriol 
finds no saturation ; so that such a bath finally contains an ex- 
cess of acid which for the production of good deposits must 
from time to time be removed, if it is not preferred to throw 
the bath away and make a fresh one. The simplest method of 
removing the excess of acid is to add to the bath pure copper 
carbonate as long as strong effervescence takes place, blue 
vitriol being thereby formed, and hence the bath at the same 
time strengthened. Some operators remove the excess of acid 
by adding to the bath whiting free from iron until no more 
effervescence takes place, and then filtering off from the cal- 
cium sulphate (gypsum) formed. The first-mentioned process 
is, however, preferable in every respect. 

2. Galvanoplastic Deposition by the Battery and Dynamo. 
Since it has been shown in the preceding section that a cell 
apparatus is to be considered as a Daniell element closed in 



GALVANOPLASTY (REPRODUCTION). . 419 

itself, it will not be difficult to comprehend that in economical 
respects no advantage is offered by the production of galvano- 
plastic depositions by a separate battery, because in both cases 
the chemical work is the same, and the zinc dissolved by the 
use of the Daniell or Bunsen element effects no greater quantity 
of copper deposit in the bath than the same quantity of zinc 
dissolved in the cells of the single apparatus. In other re- 
spects the use of a battery, however, offers great advantages. 
The employment of external sources of current requires the 
same arrangement as shown in Figs. 54 and 55, pp. 104 and 
105 ; copper anodes being placed in the bath, which are con- 
nected with the anode pole of the battery. 

By this arrangement, while the copper is being deposited 
upon the mould, the copper anodes become dissolved by the 
sulphuric acid set free, copper sulphate being formed, which 
continued action keeps the copper content of the bath quite 
constant. Furthermore, no foreign metallic admixtures reach 
the bath, as is the case in the single cell apparatus, by the 
white vitriol solution penetrating from the clay cell into the 
bath, and causing the formation of rough and brittle deposits 
of copper. The principal advantage, however, is that by plac- 
ing a resistance board in the circuit, the current-strength can be 
controlled so that the deposits can be quickly covered with a 
strong current, and then augmented with a weaker current, and 
that by intelligently regulating the current-strength, deep de- 
pressions can also be covered, which is effected with difficulty 
in the single-cell apparatus. 

A. Depositions with the Battery. 
The Daniell element described on p. 38, which yields a 
tension of about 1 volt, is much liked for this purpose. Since 
the copper bath for galvanoplastic purposes requires for its de- 
composition an electromotive force of only 0.5 to 1 volt, it will 
be best for slightly depressed moulds to couple the elements 
for quantity (Fig. 3, p. 20), alongside of each other; and only 
in cases where the particular kind of moulds requires a current 



420 ELECTRO-DEPOSITION OF METALS. 

of stronger tension, to couple two elements for tension one 
after the other, an excess of current being rendered innoxious 
by means of the resistance board, or by suspending larger 
surfaces. 

Bunsen elements may, however, be used to great advantage, 
since the zincs of the Daniell elements become tarnished with 
copper, and have to be frequently cleansed if the process is not 
to be retarded or entirely interrupted. The Bunsen elements 
need only be coupled for quantity, their electromotive force 
being considerably greater. To be sure, the running expenses 
are much greater than with Daniell elements, at least when 
nitric acid is used for filling. All that has been said under 
" Electro-plating arrangements in particular," p. 97, in regard 
to conducting the current, the resistance boards, conducting 
rod, anodes, etc., is also valid for plants for the galvanoplastic 
deposition of copper with the battery. 

B. Depositions with the Dynamo. 

It is best to use dynamos capable of yielding a large quan- 
tity of current with a tension of 2, or, at the utmost, 2 y 2 volts. 
In order to avoid repetition, the reader is referred to what 
has been said under " Arrangements with dynamo-electric 
machines," p. 115, the directions given there applying also to 
the galvanoplastic process. Since only in very rare cases the 
object-surface will be the same in all baths, it will be ad- 
visable to supply each of the baths, if several of them are 
worked with one dynamo, with a resistance-board and a volt- 
meter. 

Under certain conditions, coupling the baths one after the 
other may be of advantage, but in this case a dynamo of a 
correspondingly higher tension has to be used. 

Copper baths for galvanoplastic depositions with a separate 
source of current. — The directions for the composition of the 
bath vary very much, some authors recommending a copper 
solution of 1 8° Be. which is brought up to 22° Be. by the 
addition of pure concentrated sulphuric acid. Others again 



GALVANOPLASTY (REPRODUCTION). 42 I 

increase the specific gravity of the bath up to 25 ° Be. by the 
addition of sulphuric acid, while some prescribe an addition of 
5 to 7 per cent, of sulphuric acid. It is difficult to give a 
general formula suitable for all cases, because the addition of 
sulphuric acid will vary according to the current-strength at 
disposal, the nature of the moulds, and the distance of the 
anodes from the objects. The object of adding sulphuric acid 
is, on the one hand, to render the bath more conductive and, 
when used in proper proportions, to make the deposit more 
elastic and smoother, and prevent the brittleness and coarse- 
grained structure which, under certain conditions, appear. 
When depositing with a battery, somewhat more sulphuric acid 
may be added to the bath than when employing the current 
of a dynamo. The following compositions have, in most cases, 
been found suitable for the reproduction of shallow as well as 
of deep moulds. 

. I. For depositing with the dynamo r — Blue vitriol solution of 
1 8° Be. 100 quarts, pure sulphuric acid of 66° Be. 1 to 1^ 
quarts. 

II. For depositing with the battery. — Blue vitriol solution of 
1 8° Be. 100 quarts, pure sulphuric acid of 66° Be. 1^ to 2 
quarts. 

For some special uses, the composition of the bath has to 
be somewhat modified, which will be referred to later on. In 
regard to the elasticity, strength and hardness of gal vano plastic 
depositions of copper, Hiibl found that copper of great 
toughness, but of less hardness and strength, is obtained with 
a current-density of 0.6-1.0 ampere from an 18 per cent, blue 
vitriol solution, and copper of great hardness and strength, but 
of little toughness, with 2 to 3 amperes, from a 20 per cent, 
solution. 

For copper printing-plates, a 20 per cent, solution, com- 
pounded with 3 per cent, of sulphuric acid, and with the use of 
a current-density of 1.3 amperes, was found most suitable. 

Many operators prefer as a bath a solution of pure blue 
vitriol of 22° Be., without any addition of sulphuric acid. A 



422 



ELECTRO-DEPOSITION OF METALS. 



good deposit is obtained in such a bath, but a tension of 2 to 
2y 2 volts is required, while acidulated baths need only ^ to 
I y 2 volts, according to the content of acid. 

Very fine deposits have also been obtained in baths consist- 
ing of a blue vitriol solution of 21° Be., brought up to 22° by 
the addition of sulphuric acid. This shows that it is not neces- 
sary to stick to a fixed unlimited composition of the baths, 
provided it is understood how to bring the current-condition 
into harmony with the composition. 

According to the composition of the bath, a fixed minimum 
and maximum current-density corresponds to it, which must 
not be exceeded if serviceable deposits are to be obtained. 
There is, however, a further difference according to whether the 
bath is at rest or agitated. Hiibl obtained the following re- 
sults : 



Composition of solution. 



1 5 per ceut. blue vitriol, without sulphuric 

acid 

15 per cent, blue vitriol, with 6 per cent. 

sulphuric acid 

20 per cent, blue vitriol, without sulphuric 

acid . 

20 per cent, blue vitriol, with 6 per cent. 

sulphuric acid 



Minimum and maximum current-density 
per 15.5 square inches. 



With solution at 

rest. 

Amperes. 




With solution gently 
agitated. 
Amperes. 



3.9 to 5.2 

2.3 " 3-o 
5.1 " 6.8 
3.0 " 4.0 



Touching the addition of sulphuric acid, it was shown that 
no difference in the texture of the deposit is perceptible if the 
addition of acid varies between 2 and 8 per cent. 

The preceding table shows that a copper bath when gently 
agitated can stand considerably higher current-densities, and 
hence will work with correspondingly greater activity than a 



GALVANOPLASTY (REPRODUCTION). 423 

bath at rest. In the electrolytic refining of copper it was 
found that for the faultless deposition of copper the bath must 
be maintained entirely homogeneous in all its parts. When a 
copper bath is at rest, and the depositing operation is in 
progress, the upper layers of the bath become poorer in cop- 
per than the lower, while at the same time they contain more 
sulphuric acid. This difference in the composition of the 
upper and lower layers has the disadvantage that the portions 
dipping into the layers richer in copper become more thickly 
coppered than those in the upper layers. Baths which are con- 
stantly gently agitated show less inclination to the formation of 
knots and other rough excrescences, and hence the current- 
density may be greater than with solutions at rest, the result 
being that deposition is effected with greater rapidity. These 
experiences gathered in electro-metallurgical operations on a 
large scale, have been advantageously applied to galvanoplasty. 

Constant agitation of the copper-bath may be effected in 
various ways. A mechanical stirring contrivance may be pro- 
vided, or agitation may be effected by blowing in air, or finally, 
by the flux and reflux of the copper solution. 

With the use of a stirring apparatus, stirring rods of hard 
rubber or glass which are secured to a shaft running over the 
bath, swing like pendulums between the electrodes. This 
motion of the shaft is effected by means of leverage driven 
from a crank pulley. The stirring rods should not move with 
too great rapidity, otherwise the slime from the anodes, which 
settles in the bath, might be stirred up. 

If the bath is to be agitated by blowing in air, the latter is 
forced in by means of a pump through perforated lead pipes 
arranged horizontally about two inches from the bottom of the 
tank. 

Agitation of the bath by flux and reflux of the solution may 
be effected in various ways, and is especially suitable where 
many copper baths are in operation. 

The baths are arranged in the form of steps. Near the 
bottom each bath is provided with a leaden outlet-pipe (Fig. 



424 



ELECTRO- DEPOSITION OF METALS. 




144), which terminates over the 
next bath over a distributing 
gutter, or as a perforated pipe, 
h. From the last bath the cop- 
per solution flows into a reser- 
voir, £, from which it is forced 
by means of a hard-rubber 
pump, i f into the reservoir, A, 
placed at a higher level. From 
A it again passes through the 
baths B, C, and D. A leaden 
steam coil may, if necessary, be 
placed in A, to increase the 
temperature, if it should have 
become too low. Over A a 
wooden frame covered with felt 
may be placed ; the copper 
solution flowing upon the frame 
and passing through the felt 
is thereby filtered. 

Annealed sheets of the purest 
electrolytic copper are used as 
anodes. Impure anodes intro- 
duce other metallic constituents 
into the bath, and the result 
might be a brittle deposit. The 
use of old copper boiler sheets, 
so frequently advocated, is de- 
cidedly to be rejected. 

The more impurities the 
anodes contain the darker the 
residue formed upon them will 
be, and this residue in time de- 
posits as slime upon the bottoms 
of the tanks. Anodes of electro- 
lytic copper also yield a residue, 



GALVANOPLASTY (REPRODUCTION). 425 

which, however, is of a pale brown appearance, and consists of 
cuprous oxide and metallic copper. It is recommended daily 
to free the anodes from adhering residues by brushing, so as to 
decrease the collection of slime in the bath. 

The anode surfaces should be at least equal to that of the 
moulds, and for shallow moulds the distance between them and 
the anodes may be from 2 to 3 inches, but for deeper moulds it 
must be increased. 

The copper withdrawn from the bath by deposition is only 
partially restored, but not entirely replaced, by the anodes, 
and hence the content of copper will in time decrease, and the 
content of free acid increase. The deficiency of copper can, 
however, be readily replaced by suspending bags filled with 
blue vitriol in the bath, while too large an excess of acid is 
removed by the addition of copper carbonate. 

However, in order not to grope in the dark in making such 
corrections of the bath, it is necessary to determine from time 
to time the composition of the copper solution as regards the 
content of copper and acid, for which purpose the methods de- 
scribed below may be used. 

Examination of the Acid Copper Baths. 

Determination of Free Acid. — The free acid is determined by 
titrating the copper solution with standard soda solution, congo- 
paper being used as an indicator. Bring by means of a 
pipette, 10 cubic centimeters of the copper bath into a beaker, 
dilute with the same quantity of distilled water, and add drop 
by drop from a burette standard soda solution, stirring con- 
stantly, until congo-paper is no longer colored blue, when 
moistened with a drop of the solution in the beaker. Since 1 
cubic centimeter of standard soda solution is equal to 0.049 
gramme of free sulphuric acid, the cubic centimeters of stan- 
dard soda solution used multiplied by 4.9 give the number of 
grammes of free sulphuric acid per liter of bath. 

Volumetric determination of the content of copper according to 
Haen's method. — This method is based upon the conversion of 



426 ELECTRO-DEPOSITION OF METALS. 

blue vitriol and potassium iodide into copper iodide and free 
iodine. By determining the quantity of separated free iodine 
by titrating with solution of sodium hyposulphite of known 
content, the content of blue vitriol is found by simple calcu- 
lation. The process is as follows : Bring 10 cubic centimeters 
of the copper bath into a measuring flask holding T V liter, 
neutralize the free acid by the addition of dilute soda lye until 
a precipitate of bluish cupric hydrate, which does not disap- 
pear even with vigorous shaking, commences to separate. 
Now add, drop by drop, dilute sulphuric acid until the pre- 
cipitate just dissolves ; then fill the measuring flask up to the 
mark with distilled water, and mix by vigorous shaking. Of 
this solution bring 10 cubic centimetres by means of a pipette 
into a flask of ioo cubic centimetres' capacity and provided 
with a glass stopper ; add 10 cubic centimetres of a 10 per 
cent, potassium iodide solution, dilute with some water, and 
allow the closed vessel to stand about 10 minutes. Now add 
from a burette, with constant stirring, a decinormal solution of 
sodium hyposulphite until starch-paper is no longer colored 
blue by a drop of the solution in the flask. Since I cubic 
centimetre of decinormal solution corresponds to 0.0249 
gramme of blue vitriol (=0.0063 gramme of copper), the 
content of blue vitriol in one liter of the solution is found by 
multiplying the number of cubic centimetres of decinormal 
solution used by 24.9. For the correctness of the result it is 
necessary that the copper bath should be free from iron. 

The electrolytic determination of the copper being more simple, 
it is to be preferred to the volumetric method. Bring by means 
of the pipette 10 cubic centimetres of the copper bath into 
the previously weighed platinum dish, add 2 cubic centimetres 
of strong nitric acid, fill the dish up to within 1 centimetre of 
the rim with distilled water, and electrolyze with a current- 
strength ND 100= 1 ampere. 

Deposition of copper is finished when a narrow strip of pla- 
tinum sheet placed over the rim of the dish and dipping into 
the fluid shows in 10 minutes no trace of a copper deposit, 



GALVANOPLASTY (REPRODUCTION). . 427 

which is generally the case in 3^ hours. The deposit is then 
washed without interrupting the current, rinsed with alcohol 
and ether, and dried for a short time at 21 2° F. in the air bath. 
The increase in weight of the platinum dish multiplied by 100 
gives the content of metallic copper in grammes per 1 liter of 
bath. To find the content of blue vitriol, multiply the found 
content of copper per liter by 3.92, or multiply the content of 
copper determined in 10 cubic centimeters of bath by 392. 

If now the content of free acid and of the blue vitriol in the 
bath has been ascertained, a comparison with the contents 
originally present in preparing the bath will show how many 
grammes per liter the content of acid has increased, and how 
many grammes the content of copper has decreased, Then by 
a simple calculation it is found how much dry pure copper 
carbonate has to be added per liter of solution to restore the 
original composition. For each gramme more of sulphuric 
acid than originally present, 1.26 grammes of copper carbonate 
have to be added, and each gramme of copper carbonate in- 
creases the content of blue vitriol 2.02 grammes per liter of 
bath. By reference to these data the operator is enabled to 
calculate whether the quantity of copper carbonate added for 
the neutralization of the excess of free acid suffices to restore 
the original content of blue vitriol ; or whether, and how much, 
blue vitriol per liter has to be added. 

With the use of baths in which the solutions circulate, the 
additions are best made in the reservoir placed at a higher 
level, into which the solution constituting the bath is raised 
by means of a pump. The composition of such baths, con- 
nected one with the other, is the same, and a single determina- 
tion of the content of copper and free sulphuric acid will 
suffice. However, with baths the contents of which do not 
circulate and are not mixed, a special determination has to be 
made for each bath and the calculated additions have to be 
made to each separate bath. 

Preparation of moulds (matrices) in plastic material. — If a 
negative of the original for the production of copies is not to 



428 ELECTRO-DEPOSITION OF METALS. 

be made by direct deposition upon a metallic object, the nega- 
tive has to be prepared by moulding the original in a plastic 
mass, which on hardening will retain the forms and lines of 
the design to the finest hatchings. Gutta-percha, wax (stearine, 
etc.), plaster of Paris, glue, and a few readily fusible metals are 
suitable materials for this purpose. 

Since the galvanoplastic process, as far as it applies to electro- 
typing ', will next be considered, we first direct our attention to 
the preparation of moulds or matrices of gutta-percha and 
wax, the only materials suitable for this purpose, and which are 
generally used. 

I. Moulding in gutta-percha. — For the reproduction of the 
fine lines of a wood-cut or copper-plate, pure gutta-percha 
freed by various cleansing processes from the woody fibres, 
earthy substances, etc., found in the crude product, is very 
suitable. Besides the requisite degree of purity, the gutta- 
percha should possess three other properties, viz., it must be- 
come highly plastic by heating, without, however, becoming 
sticky, and finally it should rapidly harden. 

The most simple way of softening gutta-percha is to place 
it in water of 176 to 194 F. When thoroughly softened no 
hard lumps should be felt in kneading with the hands, in doing 
which the latter should be kept thoroughly moistened with 
water. A fragment corresponding to the size of the object to 
be moulded is then rolled into a plate about ^ to ^ inch 
thick. To facilitate the detachment of the mould after cooling, 
the surfaces of the objects to be moulded, as well as the side 
of the gutta-percha which is to receive the impression, should 
be well brushed with black lead (plumbago or graphite). The 
black-leaded surfaces are then placed one upon the other, and 
after gently pressing the gutta-percha with the hand upon the 
original the whole is placed in the press. To stop the further 
movement of the press-plate and prevent injury to the mould 
by too strong a pressure, small iron blocks, somewhat higher 
than the frame containing the object to be moulded and the 
gutta-percha plates, are placed on both sides of the frame. 



GALVANOPLASTY (REPRODUCTION). . 429 

The screw of the press is then made to act until the press- 
plate touches the iron blocks. Under this pressure the gutta- 
percha is allowed to cool and harden. 

For making the impression of the form in the moulding 
composition, a moulding press is used which is capable of giv- 

Fig. 145. 




ing a gradual and powerful pressure. Fig. 145 represents a 
form of moulding press in common use, and known as the 
" toggle " press. It consists of a massive frame having a planed 
movable bed over which a head is swung on pivots and counter- 
balanced by a heavy weight, as shown, so that it can be readily 



430 



ELECTRO-DEPOSITION OF METALS. 



thrown up, leaving the bed exposed, the black-leaded type- 
form being placed on the bed. The well black-leaded case is 
attached by clamps to the movable head, or the form (also 
black-leaded) is laid face down on the case, and the head is 
then turned down and held in place by the swinging bar 
(shown turned back in the cut). All being ready, the toggle- 
pressure is put on by means of the hand-wheel and screw, 
the result being to raise the bed of the press with an enormous 

Fig. 146. 




pressure, causing the face of the type-form to impress itself 
into the exposed moulding surface. 

Fig. 146 represents a form of "hydraulic press" less com- 
monly used than that just described. It is provided with 
projecting rails and sliding plate, on which the form and case 
are arranged before being placed in the press. The pump, 
which is worked by hand, is supported by a frame-work on 



GALVANOPLASTY (REPRODUCTION). 43 I 

the cistern below the cylinder, and is furnished with a grad- 
uated adjustable safety-valve to give any desired pressure. 

2. Moulding in wax (stearine). — Beeswax is a very useful 
material for preparing moulds, but, like stearine, it is according 
to the temperature now softer and now harder, which must be 
taken into consideration. In the cold, pure beeswax is quite 
brittle and apt to become full of fissures in pressing. To de- 
crease the brittleness certain additions are made to the wax. 
Urquhart recommends the following mixture, which is frequently 
used in England: Beeswax 85 parts by weight, Venice tur- 
pentine 13, black-lead finely pulverized 2. 

According to Volkmer, a good mixture is obtained by melt- 
ing together 70 parts of wax and 30 of stearine. Watt prefers 
a mixture consisting of 70 parts of wax, 26 of stearine, and 4 
of litharge or flake-white. G. L. v. Kress recommends the fol- 
lowing mixture: White wax 42.32 ozs., Syrian asphalt 14. 11 
ozs., stearine 14. 11 to 21.16 ozs., tallow 10.58 ozs., graphite 
1.76 ozs. First melt the asphalt over a moderate fire, then add 
the wax, stearine and tallow, and when these are melted, the 
graphite ; stir until the mixture begins to congeal. 

To prepare the wax mould pour the melted composition into 
flat metallic trays provided with loops for suspension in the 
bath. When the composition is nearly set remove any bubbles 
of air or impurities from the surface with blotting-paper. After 
black-leading the surface, press the original, also black-leaded, 
upon the composition and submit the whole to pressure until 
cold. When the black-leading has been carefully done there 
is no difficulty in detaching the original after cooling. Many 
operators slightly oil the surface of the original instead of 
black-leading. 

When the mould of gutta-percha or wax has been properly 
made, it is thoroughly black-leaded in order to give it a con- 
ducting surface upon which the electro-deposition of the copper 
may take place. Black-leading must be very thorough so that 
the black-lead penetrates into every line and letter of the 
mould, otherwise the copper deposited on the surface will be 



432 



ELECTRO-DEPOSITION OF METALS. 



an imperfect copy of the original, and it will be useless to place 
the mould in the bath. The black-lead used in every stage 
of the electrotyping process must be of the purest descrip- 
tion and in the most minute state of division. The best 
material for the purpose is prepared from the purest selected 

Fig. 147. 




Ceylon graphite, which is ground by rolling with heavy iron 
balls until it is reduced to a dead-black, impalpable powder. 

Black-leading the moulds is performed either by hand or 
more commonly by machines. 

Fig. 147 shows one of these machines with its cover re- 
moved to exhibit its construction. It has a traveling carriage 



GALVANOPLASTY (REPRODUCTION). 



433 



holding one or more forms, which passes backward and for- 
ward, under a laterally vibrating brush. Beneath the machine 
is placed an apron which catches the powder, which is again 
used. 

Another construction of a black-leading machine is shown 
in Fig. 148, the details of which will be understood without 
lengthy description. The moulds are placed upon the slowly 
revolving, horizontal wheel upon which the brush moves 

Fig. 148. 




rapidly up and down with a vertical, and at the same time" 
lateral, vibrating motion. The black-leading space being closed 
air-tight, scattering of black-lead dust is entirely prevented, 
the excess of black-lead collecting in a vessel placed in the 
pedestal. 

On account of the dirt and dust caused by the dry process 
of black-leading, some electrotypers prefer the wet process in- 
vented by Mr. Silas P. Knight, of New York. This process 
28 



434 ELECTRO-DEPOSITION OF METALS. 

is designed to work more quickly and neatly, producing 
moulds that are thinly, evenly and perfectly covered. The 
moulds are placed upon a shelf in a suitable receptacle, and a 
rotary pump forces an emulsion of graphite and water over 
their surfaces through a traveling fine-rose nozzle. This pro- 
cess is pronounced to be rapid, efficient, neat and economical. 

With very deep forms of type, it is sometimes of advantage 
to first coat the black-leaded surface with copper, in order to 
obtain a uniform deposit in the bath. The process is as fol- 
lows : Pour alcohol over the black-leaded form, let it run off 
and then place the form horizontally over a water trough. 
Now pour over the form blue vitriol solution of 15 to 16 Be., 
dust upon it from a pepper-box some impalpably fine iron 
filings and brush the mixture over the whole surface, which 
thus becomes coated with a thin, bright, adherent film of 
copper. Should any portion of the surface after such treat- 
ment remain uncoppered, the operation is repeated. The 
excess of copper is washed off and the form, after being 
provided with the necessary conducting wires, is ready for the 
bath. 

Gilt or silvered black-lead is also sometimes used for very 
deep forms. It is, however, cheaper to mix the black-lead 
with y^ its weight of finest white bronze powder from finely 
divided tin. When forms thus black-leaded are brought into 
the copper bath, the particles of tin become coated with 
copper, also causing a deposit upon the black-lead particles in 
contact with them. 

After black-leading the workman takes one or several stout 
copper wires, the ends of which, after thorough cleansing, he 
heats for an instant, and imbeds them in the wax on the side of 
the mould. The surface of this wire is carefully exposed, and 
by way of precaution the place is rubbed with black-lead with 
the finger to restore the black-lead surface that may have been 
disturbed. Trifling as this circumstance of exposing the im- 
bedded wire may appear, the galvanic deposit of the copper 
on the face of the mould would be impossible were it neglected, 



GALVANOPLASTY (REPRODUCTION). 435 

as the mass of wax being a non-conductor of electricity a gal- 
vanic current could not otherwise be established. The expos- 
ure of the wire, therefore, is essential in order that the surface 
of the mould may be rendered properly conductive to insure 
the uniform deposition of copper upon it. To confine the de- 
posit of copper where it is actually desired, and to prevent it 
from unnecessarily spreading over the edges of the mould, a 
tool called the "building iron" is heated and run over the 
mould so as to destroy the continuity of the black-lead surface, 
save where the deposit of copper is wanted. 

In order that the deposition of copper may be as nearly uni- 
form in thickness as possible over the entire surface of the 
mould, it becomes necessary, where a large surface is to be 
coated, to provide as much metallic surface as possible on 
which the deposit of copper may commence and spread. One 
method of accomplishing this, is to attach one or more pieces 
of metal to the wax on the edges of the mould, and connect 
them with the slinging wires by good metallic connections. 

A very practical device in this connection is the " electric- 
connection gripper" of Messrs. R. Hoe & Co., of New York. 
This arrangement is designed to hold and sustain the moulding 
case, and at the same time to make an electric connection with 
the prepared conducting face of the mould only ; consequently, 
leaving the metal case itself entirely out of the current, so that 
no copper can be deposited on it. 

Gutta-percha being specifically lighter than water, moulds 
of this material have to be provided with a piece of heated 
lead stuck to the back to prevent them from floating, and to 
force them to occupy a perpendicular position opposite to the 
anodes. 

The moulds are suspended in the bath in the same manner 
as in other galvanic processes, special care being had that 
their surfaces hang parallel to the anodes, so that all portion 
may receive a uniform deposit. Before placing the mould in 
the bath, pour over it, while in a horizontal position, a mixture 
of equal parts of alcohol and water. By this means, a uniform 



436 ELECTRO-DEPOSITION OF METALS. 

moistening of the mould in the bath is attained, and the settle- 
ment of air-bubbles on it prevented. 

For the production of a dense, coherent and elastic deposit 
in the acid-copper bath, the chief requisite is to have the 
current-strength in the correct proportion to the surface to be 
coated, this applying to deposition with the single-cell appar- 
atus, as well as with an external source of current. 

The stronger the sulphuric acid in the clay cells of the 
simple apparatus is, with the greater rapidity it acts upon the 
zinc plates, and the more quickly is the copper deposited 
upon the moulds. If the zinc surface of the clay cells is very 
large in proportion to the surface of the moulds, the deposi- 
tion of copper also takes place with correspondingly greater 
rapidity. However, a rapid deposition of copper is to be 
avoided, if deposits possessing the above-mentioned desirable 
properties are to be obtained, because a deposit forced too 
much turns out incoherent, lacking in density, is frequently 
blistered, and, with too strong action, is even pulverulent. 
The color of the deposit furnishes a certain criterion for its 
quality; a red-brown color indicating an unsuitable deposit, 
and a beautiful rose color a good serviceable one. 

One part of concentrated sulphuric acid of 66° Be. to 30 of 
water has formerly been given as the proper proportions for 
the dilute acid used for filling the clay cells, provided the zinc 
surface be about the same as that of the moulds. If the zinc 
surface is smaller than that of the moulds, stronger acid may 
be used ; but if it is larger, the acid will have to be more dilute. 
The correct concentration of the acid in the clay cells may be 
readily determined by the progressive result of the deposit and 
its color. Deep moulds require a stronger current, and hence 
acid of greater strength than shallow moulds. However, if after 
such deep moulds are provided with a preliminary deposit, the 
current proves too strong for the correct progress of the oper- 
ation, its action may be weakened by either diluting the acid in 
the clay cells with water, or by taking out a few zinc plates, or 
by hanging a few copper sheets upon the object-rods, or sus- 
pending more moulds. 



GALVANOPLASTY (REPRODUCTION). 437 

For the deposition of copper with a separate source of cur- 
rent (battery or dynamo), the same that has been said above 
applies as regards the current-strength, which must be brought 
to a suitable degree by the resistance board. The most suit- 
able current-density for the production of a good deposit is 1.5 
to 2 amperes per i$}4 square inches of surface of moulds for 
baths for depositions with a separate source of current, given 
on page 421, if at rest, and 2 to 3 amperes if agitated. 

Since even for deeper moulds a tension of 1.5 volts suffices, 
if the bath is acidulated, the more powerful Bunsen elements 
will have to be coupled alongside one another, but two of the 
weaker Daniell or Lallande elements one after the other, and of 
such groups, as many as are required will have to be coupled 
alongside one another for quantity of current (see page 20), to 
make the active zinc surface nearly equal to that of the moulds. 
However, for shallow moulds coupling the separate weaker ele- 
ments alongside one another is also sufficient. When the 
moulds are coated with copper on every side, and also the 
deeper portions, the current is weakened if a copper deposit of 
pulverulent or coarse-grained structure and of a dark color 
should appear on the edges of the moulds, and it is feared that 
the deposit upon the design or type might also turn out pul- 
verulent. The current, however, should only be sufficiently 
weakened to prevent a further progress of the dark deposit on 
the edges towards the interior of the surface of the mould. If, 
however, by too strong a current the separation of a pulveru- 
lent deposit upon the design has already taken place, the de- 
posit may generally be saved, if the fact is noticed in time, and 
the current correspondingly weakened, as the layers are firmly 
united by the coherent copper then deposited. 

The current of the dynamo must also be sufficiently weak- 
ened by the resistance board in front of the bath, or by that 
of the machine, to guarantee the good quality of the deposit. 
For deeper moulds the tension for covering may amount to 1 
or 1.5 volts, and for very deep and steep moulds to 1.5 or 2 
volts. But when the moulds are completely covered the cur- 



438 ELECTRO-DEPOSITION OF METALS. 

rent is reduced to about 0.75 volt,* and the operation finished 
with this tension. 

The average time required for the production of a suffi- 
ciently heavy deposit with the dynamo is from 7 to 8 hours. 
In this time the deposit acquires a thickness of about j£ 
millimetre (0.013 inch), which corresponds to a weight of 
about 25 grammes (14. 11 drachms) of copper per 15^ square 
inches. 

For the production of an electrotype in a very short time, 
baths have been recommended which are prepared with copper 
nitrate in place of blue vitriol, and to which has been added 
ammonium chloride to increase their conducting power. In- 
dependent of the fact that such baths are suitable only for very 
shallow moulds, the deposit obtained with them is inferior in 
quality to that with blue vitriol baths. Besides, by the forma- 
tion of ammonia the bath becomes alkaline and turbid, and 
requires frequent corrections, which is certainly not desirable 
for regular working. 

When, as is frequently the case, an electrotype has to be 
finished and delivered in a hurry, the work may have to be 
continued during the night. However, it is frequently not 
desirable to have the dynamo running all night, and hence re- 
course will have to be had either to a cell apparatus or an 
accumulator. With the use of a cell apparatus it is advisable 
first to coat the moulds rapidly with the current from the 
dynamo, and then to finish the deposit by suspending them 
in the apparatus. 

In modern times, accumulators which have been described 
on p. 87 et seq.y are successfully employed for the purpose. 

For the galvanoplastic deposition of copper an interruption 
of the process is frequently of great disadvantage, since a 
further deposit often adheres badly to one previously formed, 
the result being blisters or that the deposit peels off. 

If, besides a dynamo, an accumulator is to be used, it has 

♦These proportions of current refer to formulae I. and IT. given on p. 421. 



GALVANOPLASTY (REPRODUCTION). 439 

first to be decided for how large a surface of deposition and 
for how long a time it is to be employed. From this the 
capacity of the accumulator, which is expressed by its work in 
ampere-hours is calculated. It will further be known what 
current in amperes and how many hours will be required for 
charging the accumulator. If, on the other hand, the maxi- 
mum surface operated upon in the baths with the direct dynamo- 
current is known, the required power of the dynamo which 
has to be procured for deposition and occasional charging of 
the accumulator will be readily ascertained. 

A dynamo with a tension of about 3 volts should be selected, 
since the charging of the accumulator requires, towards the end 
of the operation, a tension of 2.5 volts. 

Detaching the deposit or shell from the mould. — When the 
mould has received a suitable deposit, it is taken from the 
bath, rinsed in water, and all edges which might obstruct the 
detachment of the deposit from the mould are removed with a 
knife. From gutta-percha moulds the deposit is gradually 
lifted by inserting under one corner a flat horn plate, or a thin 
dull brass blade, and applying a very moderate pressure. 
Particles of gutta-percha which may remain adherent are care- 
fully burnt off over a flame. Wax moulds are placed in an 
inclined position, and a stream of hot water is poured over the 
copper surface, by which means the wax is sufficiently softened 
to allow the shell of copper to be stripped off. This may be 
done by taking hold of one corner of the shell and quickly 
lifting it as the hot water flows over it. In removing the shell 
care should be taken to keep it straight, as otherwise it will be 
difficult to back and finish it properly. 

In larger establishments a cast-iron casting and melting 
table, such as is shown in Fig. 149, is used for wax moulds. 
The planed table plate is hollow, and by means of tongues 
cast to the plate the steam which is introduced is forced to 
uniformly heat the entire plate. The electros are placed upon 
the plate, wax side down. The wax melts and runs through 
stop-cocks on the side into a copper kettle with double walls 



440 



ELECTRO-DEPOSITION OF METALS. 



which can be heated by steam for melting the wax. The iron 
ledges screwed upon the table-plate are made tight with as- 
bestos paper, so that the wax cannot run off except through 
the stop-cocks. 

If the table is to be used for casting the wax plates, cold 
water, instead of steam, is allowed to circulate through the 
hollow table plate, whereby rapid congealing of the wax is 
effected. 

Two such kettles are required, since the wax which has been 

Fig. 149. 




in contact with the bath has to be for several hours heated in 
one of the kettles to render it free from water, before it can be 
again used for casting. The wax freed from water is brought 
into the kettle and used for casting wax plates. 

Backing the deposit or shell. — The tinning of the back of the 
shell is the next operation, and has for its object to strengthen 
the union between the shell and the backing metal. For this 
purpose the back of the shell is cleansed by brushing with 
" soldering fluid," made by allowing hydrochloric acid to take 



GALVANOPLASTY (REPRODUCTION) 



441 



up as much zinc as it will dissolve, and diluting with about J^ of 
water, to which some sal ammoniac is sometimes added. Then 
the shell, face down, is heated by laying it upon an iron solder- 
ing plate, floated on a bath of melted stereotype metal, and, 
when hot enough, melted solder (half lead and half tin) is 
poured over the back, which gives it a clean, bright, metallic 
covering. Or, the shell is placed downward in the backing- 

Fig. 150. 




pan, brushed over the back with the soldering fluid, alloyed 
tinfoil spread over it, and the pan floated on the hot backing 
metal until the foil melts and completely covers the shell. 
When the foil is melted the backing pan is swung on to a 
leveling stand, and the melted backing metal is carefully 
poured on the back of the shell from an iron ladle, commenc- 
ing at one of the corners and gradually running over the sur- 



442 ELECTRO-DEPOSITION OF METALS. 

face until it is covered with a backing of sufficient thickness. 
Another method is as follows : After tinning the shell it is 
allowed to take the temperature of the backing metal on the 
floating iron plate. The plate is then removed from the melted 
metal, supported in a level position on a table having project- 

Fig. i;i. 




ing iron pins on which it is rested, and the melted stereotype 
metal is carefully ladled to the proper thickness on the back of 
the tinned shell. This process is called " backing." The thick- 
ness of the metal-backing is about an eighth of an inch. A 
good composition for backing metal consists of lead 90 parts, 
tin 5, and antimony 5. 



GALVANOPLASTY (REPRODUCTION). 



443 



Finishing, — For this purpose the plates go first to the saw 
table (Fig. 150), for the removal of the rough edges by means 
of a circular saw. The plates are then shaved to take off any 
roughness from the back and make them of even thickness. 
In large establishments this portion of the work, which is very 
laborious, is done with a power planing or shaving machine, 
types of which are shown in Figs. 151 and 152, Fig. 151 being 
a shaving machine with steam one way, and Fig. 152 one with 

Fig. 152. 




steam both ways. The flatness of the plates is then tested 
with a straight edge and any unevenness rectified by gentle 
blows with a polished hammer, taking care that the face be 
not damaged. The plate then passes to the hand-shaving 
machine, where the back is shaved down to the proper thick- 
ness, smooth and level. The edges of the plate are then 
planed down square and to a proper size, and finally the plates 
are mounted on wood type-high. Book-work is generally not 



444 ELECTRO-DEPOSITION OF METALS. 

mounted on wood, the plates being left unmounted and finished 
with beveled edges, by which they are secured on suitable 
plate-blocks of wood or iron supplied with gripping pieces, 
which hold them firmly at the proper height and enable them 
to be properly locked up. 

Finally, it remains to say a few words about the process by 
which a copy may be directly made from a metallic surface 
without the interposition of wax or gutta-percha. If the me- 
tallic surface to be moulded were free from grease and oxide, 
the deposit would adhere so firmly as to render its separation 
without injury almost impossible. Hence, the metallic original 
must first undergo special preparation, so as to bring it into a 
condition favorable to the detachment of the deposit. This is 
done by thoroughly rubbing the original with an oily rag, or, 
still better, by lightly silvering it and exposing the silvering for 
a few minutes to an atmosphere of sulphuretted hydrogen, 
whereby silver sulphide is formed, which is a good conductor, 
but prevents the adherence of the deposit to the original. 
For the purpose of silvering, free the surface of the metallic 
original (of brass, copper, or bronze) from grease, and pickle 
it by washing with dilute potassium cyanide solution (i part 
potassium cyanide to 20 water). Then brush it over with a 
solution of 4^ drachms of silver nitrate and 1 oz. 6 drachms 
of potassium cyanide (98 per cent.) in one quart of water; or, 
still better, immerse the original for a few seconds in this bath, 
until the surface is uniformly coated with a film of silver. The 
production of the layer of silver sulphide is effected according 
to the process described later on. The negative thus obtained 
is also silvered, made yellow with sulphuretted hydrogen, and 
a deposit of copper is then made, which represents an exact 
copy of the original. Instead of sulphurizing the silvering 
with sulphuretted hydrogen, it may also be iodized by washing 
with dilute solution of iodine in alcohol. The washed plate, 
prior to bringing it into the copper bath, is for some time 
exposed to the light. 

To prevent the separation of copper on the back of the me- 



GALVANOPLASTY (REPRODUCTION). 445 

tallic original to be copied, it is coated with asphalt lacquer, 
which must be thoroughly dry before bringing into the bath. 
When the deposit of copper is of sufficient thickness, the plate 
is taken from the bath, rinsed in water, and dried. The edges 
are then trimmed off by filing or cutting to facilitate the sepa- 
ration of the shell from the original. 

Of course only metals which are not attacked by the acid 
copper solution can be directly brought into the bath. Steel 
plates must therefore first be thickly coppered in the alkaline 
copper bath, and even this precaution does not always protect 
them from corrosion. It is therefore better to produce in 
a silver bath (formula I., p. 295) a copy in silver of sufficient 
thickness to allow of the separation of both plates. The silver 
plate is iodized, and from it a copy in copper is made by the 
galvanoplastic process. The copper plate thus obtained is an 
exact copy of the original, and after previous silvering, the de- 
sired number of copies may be made from it. 

Electro- etching. — The lines produced by the ordinary process 
of etching actually represent, when viewed under the micro- 
scope, a continuous series of irregular depressions and small 
cavities, and when some depth is required they are apt to be 
corroded underneath, and to increase so much in width that the 
plates are frequently spoiled. None of these objections applies 
to the galvanic process of etching, which is the invention of 
Thomas Spencer. Each line, when viewed under the micro- 
scope, represents a perfect furrow, and is just rough enough — 
for instance, in the preparation of printing plates — to hold the 
printing ink. Lines of considerable depth may be produced 
without the danger of extending in width or corroding under- 
neath. The corners of the intersection of two lines are as 
sharp as if the lines were engraved. A chief requisite for 
electro-etching is a good etching ground, since it may fre- 
quently happen that the latter may answer very well for the 
ordinary process, but is not capable of offering sufficient re- 
sistance to the electric current. A great advantage in electro- 
etching is that the solvent is always of the same strength, and, 



446 ELECTRO-DEPOSITION OF METALS. 

therefore, constant in its action, and that there is no evolution 
of acid vapors which are injurious to the respiratory organs. 

The operation of electro-etching is conducted as follows : A 
conducting wire is soldered with tin solder to the object, and 
the latter is then coated with the etching ground. The design 
is then traced with a graver, taking care that the tool lays bare 
the metal in all the lines. The object thus prepared is con- 
nected with the positive pole and suspended in the bath, while 
a plate of the same metal as the object is secured to the nega- 
tive pole. The bath consists of a dilute acid corresponding to 
the metal of the object. For silver, dilute nitric acid is used ; 
for gold and platinum, water acidulated with aqua regia; for 
copper, brass and zinc, water acidulated with sulphuric acid ; 
and for tin, water acidulated with hydrochloric acid. Baths 
containing the metal to be etched in solution, however, work 
better than acids diluted with water. Thus, for gold and plat- 
inum, gold chloride and platinic chloride are used ; for silver, 
solution of silver nitrate ; for copper and brass, solution of blue 
vitriol; for iron and steel, solution of green vitriol, or of 
ammonium chloride, or a combination of both ; for zinc, solu- 
tion of white vitriol or of zinc chloride, etc. There are besides 
various metallic salts suitable for etching by themselves or in 
combination with the above-named salts. 

As etching ground various compositions may be employed, it 
being, however, best to use, if possible, one which can be 
readily removed. A mixture of equal parts of asphalt and 
copal varnish forms a good etching ground ; also a composi- 
tion obtained by melting together asphalt 2^ parts, wax 2, 
rosin I, and black pitch 2. However, the following composi- 
tion, which resists 25 per cent, nitric acid, is to be preferred. 
It is prepared as follows : Melt yellow wax 4 parts, Syrian 
asphalt 4, black pitch 1, and white Burgundy pitch 1. When 
the mixture boils gradually add, whilst stirring constantly, 4 
parts more of pulverized Syrian asphalt. Continue boiling 
until a sample poured upon a stone and allowed to cool breaks 
in bending. Then pour the mixture into cold water and 



GALVANOPLASTY (REPRODUCTION). 447 

shape it into small balls, which for use are dissolved in oil of 
turpentine. 

Since the current-strength is under perfect control, the etch- 
ing may be carried to any depth desired. Some portions may 
be less etched than others by taking the plate from the bath, 
and, after washing and drying, coating the portions which are 
not to be further etched with lacquer, and returning the plate 
to the bath. 

Printing plates in relief may in this manner be prepared by 
slightly etching the bared design of a copper-plate in the gal- 
vanoplastic copper bath, and then bringing the plate as object 
in contact with the negative pole, while a plate of chemically 
pure copper serves as anode. The deposited copper unites 
firmly with the rough copper of the etched plates, and after re- 
moving the etching-ground with benzine or oil of turpentine, 
the design appears in relief. 

Heliography. — By this term are understood several methods 
of printing, in which plates of asphalt, chrome gelatine, etc., 
produced by exposure to light, are used. For our purposes 
only the method is of interest by which from the negative, pro- 
duced by the action of light, a galvanoplastic reproduction — 
printing plates in high and low relief — in metal is made. The 
heliographic process invented by Pretsch and improved by 
Scamoni, consists in taking by photography a good negative of 
the engraving or other object to be reproduced, developing 
with green vitriol, reinforcing with pyrogallic acid and silver 
solution, and then fixing with sodium hyposulphite solution in 
the same manner as customary for photographic negatives. A 
further reinforcement with chloride of mercury solution then 
takes place until the layer appears light gray. Now wash 
thoroughly, and intensely blacken the light portions by pouring 
upon them dilute potassium cyanide solution. As in the photo- 
graphic process, the solution must be applied in abundance 
and without stopping, as otherwise streaks and stains are 
formed. After washing, the plate is dried, further reinforced, 
and finally coated with colorless negative varnish. From this 



448 ELECTRO-DEPOSITION OF METALS. 

negative a positive collodion picture is taken, which is in the 
same manner developed, reinforced, and fixed, the reinforce- 
ment with pyrogallic acid being continued until the picture is 
quite perceptibly raised. After careful washing, pour upon the 
plate quite concentrated chloride of mercury solution, which 
has to be frequently renewed, until the picture, at first deep 
black, acquires a nearly white color, and the lines are percept- 
ibly strengthened. Now wash with distilled water, next with 
dilute potassium iodide solution, and finally with ammoniacal 
water, whereby the picture acquires first a greenish, then a 
brown, and finally a violet-brown color. After draining, the 
plate may progressively be treated with solutions of platinum 
chloride, gold chloride, green vitriol and pyrogallic acid, the 
latter exerting a solidifying effect upon the pulverulent metallic 
deposits. The metallic relief is now ready ; the layer is slowly 
dried over alcohol, and the plate, when nearly cold, quickly 
coated with a thin rosin varnish, which, after momentary dry- 
ing, remains sufficiently sticky to retain a thin layer of black 
lead, which is applied with a tuft of cotton. The edge of the 
plate is finally surrounded with wax, and, after being wired, the 
plate is brought into the galvanoplastic copper bath to be re- 
produced. 

Electro- etching in steel for the production of dies for coins ', 
reliefs, etc. — Below an outline of Rieder's patented process is 
given, it being supposed that the subject under discussion is 
the production of a die by means of which reliefs are to be 
stamped in metal plates. 

The relief is first produced in a material readily worked, for 
instance, wood, wax, etc., and a copy of it made in plaster of 
Paris. The plaster of Paris plate, which is about j£ to ^ inch 
or more thick, is placed in a metal cylinder in such a manner 
that a plaster of Paris surface of o.n to 0.15 inch depth pro- 
jects above' the edge of the cylinder. This cylinder containing 
the plaster of Paris model is secured in a vessel containing 
solution of ammonium chloride and a metal spiral connected 
with the negative pole of the source of current. By a suitable 



GALVANOPLASTY (REPRODUCTION). 449 

mechanical contrivance the vessel together with the cylinder 
containing the model is pressed against the steel-plate con- 
nected with the positive pole. 

The process is now as follows : The porous plaster of Paris 
absorbs to saturation ammonium chloride solution. The steel 
plate first comes in contact with the highest points of relief, 
and the current becoming active, dissolves the steel on the 
point of contact. The ferrous chloride solution which is formed 
penetrates downward into the capillaries of the plaster of Paris 
so that fresh quantities of the electrolyte constantly act upon 
the steel plate. Etching thus progresses, and gradually every 
portion of the plaster of Paris model comes in contact with the 
steel plate, when etching is finished. 

However, the practical execution of the work is not so simple 
as the theoretical process above described. The carbon in the 
steel and other admixtures, such as silicon, etc., prevent uniform 
etching and must, therefore, from time to time, be mechanically 
removed from the etching surface. For this purpose the ves- 
sel containing the electrolyte together with the model, has to 
be lowered, the steel plate taken from the apparatus and 
cleansed. It will, therefore, be readily understood that ac- 
curate etching corresponding to the metal can only take place 
when the principal parts, namely, the steel plate and model, 
after cleansing, mathematically occupy exactly the same place 
and position as before, so that the model presses accurately 
against the same parts of the steel plate as in the beginning of 
the etching operation. 

Conjointly with Ur. Geo. Langbein & Co., Rieder has con- 
structed an apparatus which works with such precision as to 
fulfill all the above mentioned conditions. Cleansing of the 
steel plate is effected by means of an electrically driven circular 
brush. For further details those interested are referred to 
Geo. W. Langbein & Co., who have secured by contract the 
sole right to this process. 

Galvanoplastic reproduction of busts, vases, etc. — For this pur- 
pose an entirely different process of preparing the moulds than 
29 



45 O ELECTRO-DEPOSITION OF METALS. 

that described for electrotyping is required, the material for 
moulding depending on the nature of the original. Besides 
gutta-percha and wax, readily fusible metals, plaster of Paris,, 
and glue will have to be considered. If the original bears heat- 
ing to about 230 F., a copy in one of the readily fusible alloys 
given later on may be made. If it will stand heat and pressure, 
it is best to mould in gutta-percha ; but if neither heat nor 
pressure can be applied, the moulds will have to be executed 
in plaster of Paris or in glue. The manner of moulding and 
the material to be chosen furthermore depend on whether 
surfaces in high relief or round plastic bodies are to be copied* 
whether projecting portions are undercut, and whether the 
mould can be directly detached, or, if this is not the case,, 
whether the original has to be dissected and moulded in sepa- 
rate parts. 

Regarding the practice of moulding, the reader is referred to 
special works on that subject. Only the main points for the 
most frequently occurring reproductions will here be given. 

Surfaces in relief and not undercut are readily moulded in an 
elastic mass such as gutta-percha or wax; however, undercut 
reliefs and especially round plastic objects mostly require a 
plaster-of- Paris mould and are generally dissected. The dis- 
section, of course, is not carried further than absolutely neces- 
sary, because the separate parts must be united by a soldering 
seam, which requires careful work, and the seam itself must be 
worked over and made invisible. Hence the section should as 
much as possible be made through smooth surfaces, edges, etc., 
where the subsequent union by a soldering seam will prove 
least troublesome, while cutting through ornaments or through 
portions the accurate reproduction of which is of the utmost 
importance, should be avoided. Heads and busts are always 
executed in a core mould and in portions, unless the entire 
figure is to be deposited in one piece in a closed mould. The 
section is made either through the centre line of the head 
through the nose, which, however, makes the subsequent union 
very troublesome, if the copy is to be an exact reproduction of 



GALVANOPLASTY (REPRODUCTION). 45 I 

the original, or the mould is divided from ear to ear, which has 
the disadvantage that the deepest part of the mould correspond- 
ing to the nose receives the thinnest deposit. It has, therefore, 
been proposed to make two cuts so that three portions are 
formed ; one cut from one ear at the commencement of the 
growth of hair to the other ear ; and the second cut from one 
ear in a downward direction below the lower jaw in the joint of 
the head and neck, through this joint below the chin, and then 
upwards to the other ear, and in front of it to where the hair 
begins. In bearded male heads the cut follows the contour of 
the beard and not the joint on the neck behind the beard. 

Oil gutta-percha has the advantage of allowing moulding 
without any pressure of the largest shield-shaped or semi-cir- 
cular objects with all undercuts, which otherwise can only be 
accomplished with glue. The mould can be readily detached 
from the original as well as from the deposit, which is of great 
advantage. But, on the other hand, oil gutta-percha deteri- 
orates by frequent use, and burns to the mould when worked 
too hot, the result being that it is difficult to detach from the 
original, as well, the formation of air bubbles. However, the 
heat must neither be too slight, otherwise the sharpness of the 
impression would suffer. 

Oil gutta-percha is prepared by heating in the water bath 
100 parts of gutta-percha, 10 parts of olive oil and 2 parts of 
stearine. 

The original, preferably of copper, should be free from 
grease. It is laid upon an iron plate and the latter heated by 
a flame until the original can be just for a moment retained in 
the hand. The oil gutta-percha, previously heated in a sand 
bath aud thoroughly stirred, is then brought in a slow stream 
upon the original. After allowing the oil gutta-percha to con- 
geal superficially, the original, together with the heating plate, 
is brought into cold water, where complete congealing soon 
takes place. 

For moulding in the press or by hand with oil gutta-percha, 
the heated mass is poured into cold water and then kneaded to 
the consistency of stiff dough. 



452 ELECTRO-DEPOSITION OF METALS. 

To mould round articles in gutta-percha, the softened gutta- 
percha is kneaded with wet hands upon the oiled original, or, 
in order to avoid some portions receiving a stronger pressure 
than others, and to insure a layer of gutta-percha of uniform 
thickness upon all parts, moulding may also be executed in a 
ring or frame of iron or zinc under a press. For the rest, all 
that has been previously said in regard to moulding in gutta- 
percha is also applicable. 

The following metallic alloys have been proposed for the 
preparation of moulds : 

I. Lead 2 parts, tin 3, bismuth 5 ; fusible at 21 2° F. 
II. Lead 5, tin 3, bismuth 8 ; fusible at 185 F. 

III. Lead 2, tin 2, bismuth 5, mercury 1 ; fusible at 158 F. 

IV. Lead 5, tin 3, bismuth 5, mercury 2 ; fusible at 127.5 F. 
The advantage of metallic moulds consists in the metal being 

a good conductor of electricity, in consequence of which heavy 
deposits of greater uniformity can be produced than with non- 
metallic moulds which have been made conductive by black 
lead. Nevertheless, they are but seldom employed, on account 
of the crystalline structure of the alloys and the difficulty of 
avoiding the presence of air bubbles. Bottger claims that a 
mixture of lead 8 parts, tin 3, and bismuth 8, which is fusible 
at 227 F., shows a less coarse-grained structure. 

Fusible alloys containing mercury should not be used for 
taking casts of metallic objects — iron excepted — as these will 
amalgamate with the mercury and be injured. Moreover, 
copper deposits obtained upon such alloys are very brittle, 
which is due to the combination of the mercury with the de- 
posited copper. 

For moulding with metallic alloys place the oiled object at the 
bottom of a shallow vessel and pour the liquid metal upon it; 
or pour the liquid metal into a box, remove the layer of oxide 
with a piece of stout paper, and when the metal is just begin- 
ning to congeal, firmly press the object in it. 

Plaster of Paris is used for making casts of portions from 
originals which are so strongly undercut that a mould consist- 



GALVANOPLASTY (REPRODUCTION). • 453 

ing of one piece could not be well detached from them. For 
taking casts from metallic coins and medals or from small 
plaster reliefs, it is a very convenient material. The mode of 
procedure is as follows: After the original model, say a medal, 
has been thoroughly soaped or black-leaded, wrap round the 
rim a piece of sufficiently stout paper or thin lead foil, and 
bind it in such a manner by means of sealing wax that the 
face of the medal is at the bottom of the receptacle thus 
formed. Then place the whole to a certain depth in a layer 
of fine sand, which prevents the escape of the semi-fluid plaster 
of Paris between the rim of the medal and the paper. Now 
mix plaster of Paris with water to a thin paste, take up a small 
quantity of this paste with a pencil or brush and spread it in 
a thin film carefully and smoothly over the face of the medal, 
then pour on the remainder of the paste up to a proper height 
and allow it to set. After a few minutes the plaster heats and 
solidifies. Then remove the surrounding paper, scrape off 
with a knife what has run between the paper and the rim of 
the medal, and carefully separate the plaster cast from the 
model. If, instead of applying the first layer with a brush, 
the whole of the plaster were run at once into the receptacle, 
there would be great risk of imprisoning air bubbles between 
the model and the mould, which would consequently be worth- 
less. The mould is finally made impervious and conductive 
according to one of the methods to be described later on. 

The moulding in plaster of Paris in portions, when casts from 
large plastic objects with undercut surfaces and reliefs are to be 
taken, is troublesome work, because each separate mould must 
not only be so that it can be readily separated without injury 
to the original, but must also fit closely to its neighbors. 
Hence thought and judgment are required to see of which parts 
separate moulds are to be made, or, in other words, in how 
many parts the mould is to be made. After determining on 
the plan of the work, the mode of procedure is as follows : Oil 
a portion of the object, if it consists of metal, or soap it, if of 
plaster of Paris, marble, wood, etc., and apply by means of a 



454 ELECTRO-DEPOSITION OF METALS. 

brush a thinly-fluid paste of plaster of Paris, taking care that 
no air bubbles are formed by the strokes of the brush. When 
this thin coat is hard, continue the application of plaster of 
Paris with a horn spatula until the coat has acquired a thick- 
ness of 24 to i inch, and allow it to harden. Then separate the 
mould, and after cutting or sawing the edges square and 
smooth, replace it upon the portion of the original model cor- 
responding to it. Now oil or soap the neighboring portions of 
the model, and at the same time the smooth edges of the first 
mould which come in contact with the mould now to be made, 
and then proceed to make the second mould in precisely the 
same manner as the first. When the second mould is hard, 
trim the edges and replace it upon the model ; the same pro- 
cess being continued until the entire original model is repro- 
duced in moulds fitting well together. To prevent the finished 
moulds from falling off, and to retain them in a firm position 
upon the original model, they are tied with lead wire or secured 
with catches of brass wire or sheet. When the moulds of the 
larger portion of the model, for instance, one-half of a statue, 
are finished, the so-called case or shell is made, i. e., the backs 
of all* the moulds are coated with a layer of plaster of Paris 
which holds them together. This case is best made not too 
thin in order to attain a better resisting power. 

The entire model having been cast in the manner above de- 
scribed, and the moulds provided with the case, the whole is 
completely dried in an oven. 

The next operation is to make the plaster of Paris impervious 
to fluids, as otherwise by the moulds absorbing the acid copper 
bath, copper would be deposited in the pores of the plaster and 
the moulds be spoiled, while the copy would turn out rough 
instead of having the smooth exterior of the model. To render 
plaster of Paris and other porous substances impervious, they 
are saturated with wax or stearine or covered with a coat of 
varnish, the latter process being generally employed for large 
moulds. Apply a coat of thick linseed oil varnish to the face 
of the mould, and, after drying, repeat the process until the 



GALVANOPLASTY (REPRODUCTION). . 455 

mould is thought to be sufficiently impervious. Rendering the 
mould impervious with wax or stearine is a better and more 
complete method. For this purpose cut a groove in the rim 
of the mould, place in the groove a brass wire and twist the 
ends, which must be long enough to hold the mould by. The 
mould, having been previously dried, is then dipped into a bath 
of wax or stearine kept at a temperature of from 180 to 21 2° 
F., and a number of air bubbles will escape from the mould to 
the surface. When the production of air bubbles is consider- 
ably diminished, remove the mould from the bath, and lay it 
face up in a drying oven, whereby the melting wax in conse- 
quence of its gravity oozes down, and the face of the mould is 
ireed from an excess of wax. Whenever possible, submerging 
the entire mould should be avoided and the operation be con- 
ducted as follows : Place the heated mould in a vat filled with 
melted Wax or stearine, so that the face does not come in con- 
tact with the wax, but absorbs wax by capillarity from the back. 

The moulds thus coated with varnish or saturated with wax 
are now made conductive with black-lead, the operation being 
the same as that mentioned on p. 432. For many undercut or 
deep portions black-leading is, however, not sufficient, and re- 
course must be had to making the moulds conductive or metal- 
lizing them by the wet way. 

Metallization by the wet way. — This method consists in the 
deposition of certain metallic salts upon the moulds and their 
reduction to metal or conversion to conductive sulphur combi- 
nations. The process in general use is as follows : Apply with 
a brush upon the mould a not too concentrated solution of 
silver nitrate in a mixture of equal parts of distilled water and 
90 per cent, alcohol. When the coat is dry expose it in a 
closed box to an atmosphere of sulphuretted hydrogen. The 
latter converts the silver nitrate into silver sulphide, which is a 
good conductor of the current. For the production of the 
sulphuretted hydrogen, place in the box, which contains the 
mould to be metallized, a porcelain plate or dish filled with 
dilute sulphuric acid (1 acid to 8 water), and add five or six 



456 ELECTRO-DEPOSITION OF METALS. 

pieces of iron pyrites the size of a hazel-nut. The development 
of the gas begins immediately, and the box should be closed 
with a well-fitting cover to prevent inhaling the poisonous gas ; 
if possible, the work should be done in the open air or under a 
well-drawing chimney. The formation of the layer of silver 
sulphide requires but a few minutes, and if not many moulds 
have to be successively treated, the acid is poured off from the 
iron pyrites and clean water poured upon the latter so as not 
to cause useless development of gas. 

It has also been recommended to decompose the silver salt 
by vapors of phosphorus and to convert it into silver phosphide* 
a solution of phosphorus in bisulphide of carbon being used for 
the purpose. The layer of silver salt is moistened with the 
solution or exposed to its vapors. This method possesses, 
however, no advantage over the preceding, because, on the one 
hand, the phosphorous solution takes fire spontaneously, and, 
on the other, the odor of the bisulphide of carbon is still more 
offensive than that of sulphuretted hydrogen. 

A somewhat modified method is given by Parkes as follows : 
Three solutions, A, B, C, are required. Solution A is prepared 
by dissolving 0.5 part of caoutchouc cut up in fine pieces in 10 
parts of bisulphide of carbon and adding 4 parts of melted wax \ 
stir thoroughly, then add a solution of 5 parts of phosphorus in 
60 of bisulphide of carbon together with 5 of oil of turpentine 
and 4 of pulverized asphalt; then thoroughly shake this mix- 
ture, A. Solution B consists of 2 parts by weight of silver 
nitrate in 600 of water; and solution C of 10 parts of gold 
chloride in 600 of water. The mould to be metallized is first 
provided with wires and then brushed over with, or immersed 
in, solution A, and after draining off, dried. The dry mould is 
then poured over with the silver solution (B) and suspended 
free for a few minutes until the surface shows a dark lustre. It 
is then rinsed in water and treated in the same manner with the 
chloride of gold solution (C), whereby it acquires a yellowish 
tone, when, after drying, it is sufficiently prepared for the re- 
ception of the deposit. Care must be taken in preparing solu 



GALVANOPLASTY (REPRODUCTION). 457 

tion A, as the bisulphide of carbon containing phosphorus 
readily takes fire. 

Another method is as follows : Dissolve 5 parts by weight of 
wax in 5 of warm oil of turpentine, and add to the solution a 
mixture of 5 parts by weight of phosphorus, 1 of gutta-percha, 
5 of asphalt, in 120 of bisulphide of carbon. When both are 
thoroughly mixed, add to the whole a solution of 4 parts by 
weight of gun cotton in 60 of alcohol and 60 of ether, and after 
thoroughly shaking allow to settle. The next day pour off the 
clear solution from the sediment, when the solution can at once 
be used. It is especially well adapted for coppering parts of 
plants, leaves, flowers, etc. 

Another method of metallization is as follows : Immerse the 
leaves, etc., in iodized collodion composed of 40 per cent, 
alcohol 40 cubic centimeters, ether 60 cubic centimeters, potas- 
sium iodide I gramme, gun cotton 1 gramme. 

Allow the leaves, etc., to dry so that a firmly adhering layer 
is formed. Then immerse them in a solution of 10 parts by 
weight of silver nitrate in 100 of water, whereby a layer of silver 
iodide is formed. Now expose the article thus treated for some 
time to the light, and then immerse it in the reducing fluid 
consisting of water 500 parts by weight, green vitriol 25, and 
acetic acid of 1.04 specific gravity 2.5. The reduction of silver 
now progresses rapidly and the articles are ready for coppering. 
In employing this process it must not be forgotten that the 
layer of collodion will not stand rough usage and, hence, injury 
to it by touching with the hands and careless placing of the 
conducting wire have to be avoided. By operating with due 
care, the results are very satisfactory and sure. Instead of the 
iodized collodion, a mixture of equal parts of white of egg and 
saturated solution of common salt may be used, the remainder 
of the process being the same as above described. 

Metallization by metallic powders. — In some cases metalliza- 
tion by metallic powders is to be preferred to black-leading or 
metallizing by the wet way. Metallic or bronze powders are 
metals in a state of exceedingly fine powder, of which, for gal- 



45 # ELECTRO-DEPOSITION OF METALS. 

vanoplastic purposes, pure copper and brass powders only are 
of interest. Since such metallic powders adhere badly to waxed 
surfaces, the mould must be provided with a well-drying coat 
of lacquer, upon which, before it is completely dry, the powder 
is scattered or sifted. When the lacquer is hard a smooth sur- 
face is produced by going over the mould with a soft brush 
dipped in the metallic powder, an excess being removed by a 
thin jet of water. 

Lenoir 's process — Galvanoplastic method for originals in high 
relief. — Lenoir's method for reproducing statues in a manner 
approaches in principle to that of the foundry. He begins by 
making with gutta-percha a mould in several pieces, which are 
united together so as to form a perfect hollow mould of the 
original. This having been done, cover all the parts carefully 
with black lead. Make a skeleton with platinum wire, follow- 
ing the general outline of the model, but smaller than the 
mould, since it must be suspended in it without any point of 
contact. If the skeleton thus prepared is enclosed in the 
metallized gutta-percha mould, and the whole immersed in the 
galvanoplastic bath, it will be sufficient to connect the inner 
surface of the mould with the negative pole of the battery, and 
the skeleton of platinum wires (which should have no points 
of contact with the metallized surfaces of the mould) with the 
positive pole, in order to decompose the solution of sulphate 
of copper which fills the mould. When the metallic deposit 
has reached the proper thickness, the gutta-percha mould is 
removed by any convenient process, and a faithful copy of the 
original will be produced. Lead wires may be substituted 
for the expensive platinum wires. This method requires a 
knowledge of the moulder's art, so that good results can only 
be obtained by an experienced hand. 

Gelatine moulds. — Under certain conditions the elasticity of 
gelatine allows of the possibility of its removal from undercut 
or highly-wrought portions of the model, when it reassumes 
the shape and position it had before removal therefrom. But 
gelatine requires that the deposit shall be made rapidly, other- 



GALVANOPLASTY (REPRODUCTION). 459 

wise it will swell and be partially dissolved by too long an im- 
mersion in the copper bath. 

To make a good gelatine mould, proceed as follows : Allow 
white gelatine (cabinet-maker's glue) to swell for about 24 
hours in cold water, then drain off the water, and heat the 
swollen mass in a water bath until completely dissolved. 
Compound the glue solution with pure glycerine in the pro- 
portion of 5 to 10 cubic centimetres (0.24 to 0.3 cubic inch) 
of glycerine to 30 grammes (1.05 ozs.) of gelatine, which 
prevents the gelatine from shrinking in cooling. When some- 
what cooled off, apply the gelatine to the oiled original, which 
must be surrounded with a rim of plaster of Paris or wax, to 
prevent the gelatine from running off; when cold, lift the gela- 
tine mould from the model. Before metallizing and suspend- 
ing in the copper bath, the mould has to be prepared to resist 
the action of the latter, as otherwise it would at once swell and 
be partially dissolved before being covered with the deposit. 
This is effected by placing the mould in a highly concentrated 
solution of tannin, which possesses the property of making gel- 
atine insoluble. 

Brandley gives the following directions for preparing gelatine 
solution with an addition of tannin, which renders the moulds 
impervious to water : Dissolve 20 parts of the best gelatine in 
100 of hot water, add y 2 part of tannic acid and the same quan- 
tity of rock candy, then mix the whole thoroughly, and pour it 
upon the model. 

The same end is reached by making a mould with gelatine 
alone, then pouring an aqueous solution of 10 per cent, of 
potassium dichromate upon it, and, after draining, exposing 
the mould to the action of the sun. 

Another method is as follows : Beat into a quart of distilled 
water the whites of two eggs, filter, and cover with this liquid 
the entire surface of the gelatine mould. After drying, operate 
with the solution of potassium dichromate as in the preceding. 
By solar action the coating impregnated with dichromate is 
rendered insoluble. 



460 ELECTRO-DEPOSITION OF METALS. 

The mould must finally be metallized and, when in the bath, 
submitted to a strong current at the beginning. When the 
entire surface is covered with the copper deposit, and when 
swelling is no longer to be feared, a weaker current may be 
used. 

Below a few special uses of galvanoplasty will be briefly 
described : 

Nature printing, so named by Mr. v. Auer, Director of the 
Imperial Printing Office at Vienna, has for its object the gal- 
vanoplastic reproduction of leaves and other similar bodies. 
The leaf is placed between two plates, one of polished steel, 
the other of soft lead, and is then passed between rollers, which 
exert a considerable pressure. The leaf thus imparts an exact 
impression of itself and of all its veins and markings to the 
lead, and this impression may be electrotyped, and the copper 
plate produced used for printing in the ordinary way. Instead 
of taking the impression in lead, it is advisable to use gutta- 
percha or wax for delicate objects, which should previously be 
black-leaded or oiled. In the same manner galvanoplastic 
copies of laces, etc., may be obtained. 

The process used by Philipp for coating laces and tissues with 
copper and then silvering or gilding, belongs rather to electro- 
plating than to galvanoplasty. The tissue is saturated with 
melted wax, and after removing the excess with blotting paper 
it is made conductive by black-leading with a brush. It is, 
however, preferable to metallize such delicate objects by the 
wet way, Parke's method being especially suitable for the pur- 
pose, and also a treatment with weak solution of silver nitrate 
and pyrogallic acid frequently alternated. 

Elmore produces copper tubes by galvanoplastic deposition 
by allowing the metallic core-bar to revolve slowly between 
the anodes, while a polishing steel is by means of a mechanical 
contrivance carried with strong pressure over the deposit, 
whereby the latter is made dense and any roughness removed. 

It would seem that the process for the production of copper 
tubes, profiled hollow copper bodies, etc., patented by Ignaz 



GALVANOPLASTY (REPRODUCTION). 46 1 

Klein, is better than Elmore's method. The black-leaded or 
metallic core-bars are allowed to roll to and fro upon smooth 
or profiled plates, the so-called milling plates, or the core-bars 
are concentrically arranged around a cylindrical anode and al- 
lowed with pressure to roll on an exterior round milling sur- 
face. According to this method, the space in the baths can be 
better utilized than in the Elmore process, and the deposit 
shows excellent properties as regards uniform density and 
power of resistance. 

Corviris niello. — Corvin has invented a process of producing 
inlaid work by galvanoplasty, which has been patented, and is 
the exclusive property of J. P. Kayser & Son, of Crefeld. 
The process is as follows : A matrice of metal whose surface is 
finely polished is first made. This matrix may be used for the 
production of numerous duplicates of the same kind of object. 
The incrustrations (mother-of-pearl, glass, ivory, amber, etc.), 
are then shaped by means of a saw, files and other tools, to the 
form corresponding to that which they are to occupy in the 
design. The side of the incrustation which is laid upon the 
matrice is, as a rule, smooth. The shaped incrustations, smooth 
side down, are pasted on to the parts of the model they are to 
occupy in the design. The latter being thus produced, the 
backs of the non-metallic laminae are metallized, and the por- 
tions of the metallic plate left free are slightly oiled. By now 
placing the matrice thus prepared in the galvanoplastic bath, 
the copper is deposited, not only upon the metallic matrice, but 
also upon the back of the inlaid pieces, the latter being firmly 
inclosed by the deposited metal. When the deposited metal 
has acquired the desired thickness, it is detached from the 
matrice, and incrustations with the right side polished are thus 
obtained. The laminae are more accurately and evenly laid in 
than would be possible by the most skilled hand-work. 

Grasses, leaves, flowers, etc., may be coated with copper and 
then silvered, gilded, or platinized, by first drying them, and, 
after giving them a certain elasticity by placing in glycerine, 
metallizing them by Parkes's or some other method. 



4^2 ELECTRO-DEPOSITION OF METALS. 

Plates for the production of imitations of leather are now fre- 
quently prepared. The demand for alligator and similar 
leathers is at the present time greater than the supply, and, 
therefore, imitations are made by pressing ox-leather, the plate 
being prepared by galvanoplasty, as follows : A large piece of 
the natural skin or leather is made impervious to the bath by 
repeated coatings with lacquer, and, when, completely dry,, 
secured with asphalt lacquer to a copper or brass plate. The 
leather is then black-leaded, and, after being made conductive 
by copper wire or small lead plates, brought into the copper 
bath. When the copper deposit has acquired the desired 
thickness, the plate is further strengthened by backing with 
stereotype metal. 

To coat woody etc., with a galvanoplastic deposit of copper. — 
The absolutely dry objects are first immersed in melted wax, 
paraffine, or ceresine, and when thoroughly impregnated taken 
out and, after draining off, allowed to cool. As the impregnat- 
ing material contracts in cooling, the surface of the object is 
thereby freed from an excess of it. For this reason the ma- 
terial used for impregnating should not be made hotter than 
absolutely necessary, because the hotter it is the stronger the 
contraction or shrinkage. However, as by this contraction the 
edges and portions of the surface may become denuded of im- 
pregnating material, and thus be liable to be attacked by the 
acid copper bath, it is advisable to coat the objects, after cool- 
ing, with an acid-resisting gutta-percha lacquer prepared by 
dissolving 5 to 10 parts, by weight of gutta-percha cuttings in 
a mixture of 50 parts each of benzine and chloroform. Keep 
the solution in a wide-mouthed glass bottle provided with a 
well-fitting cork, and apply it with a brush. The solution 
being very inflammable, it should not be used near an open 
flame. 

Wooden handles of surgical instruments, etc., may be pro- 
tected from the attacks of the acid copper bath by coating 
them with a solution of wax or paraffine in ether, the latter 
after evaporating leaving a thin layer of wax upon the object. 



GALVANOPLASTY (REPRODUCTION). 463 

The articles thus prepared are black-leaded or metallized by 
Parkes's or one of the methods previously given, and brought 
into the copper bath. 

The mercury vessels of thermometers for vacuum and distilling 
apparatus are surrounded by a thick copper deposit to protect 
them from injury by mechanical force. The metallization of 
glass, porcelain, clay, terra-cotta, etc., is effected in the same 
manner as above described. 

Porcelain, pottery, stone-ware, etc., are provided with a gal- 
vanoplastic deposit of copper, according to a patent granted to 
Utzschneider & Co., by first coating the articles with a mixture 
of litharge and varnish. After drying, the litharge is rubbed 
on and the articles coppered in the galvanoplastic bath. It is 
claimed that the deposit of copper can be further provided 
with a deposit of any desired metal. The success of this pro- 
cess would seem doubtful. 

According to another method which is thoroughly reliable, 
the article is provided with a conducting layer by brushing it 
with solution of gold chloride or platinum chloride in sulphuric 
ether mixed with balsam of sulphur or oil of turpentine in 
which sulphur has been dissolved. After heating slightly, 
another heavier layer is applied with a brush. The article is 
then heated in the muffle until a lustrous metallic layer is 
formed, which is suitable, without further preparation, for 
coppering. Upon this layer of metal a galvanoplastic deposit 
of silver of any desired thickness may also be produced so 
that the deposit appears in relief. 

Galvano-plasty in iron {steel). Under " Deposition of Iron," 
the galvano-plastic production of heavy detachable deposits of 
iron has already been referred to. 

Serviceable iron electros were first produced about 1870, 
by Klein, of St. Petersburg, and used for printing Russian 
bank notes. Their preparation was, and is still, very trouble 
some, success depending on the fulfillment of many con- 
ditions, so that, notwithstanding continued experiments and the 
expense of much labor, the former expectation of entirely sup- 



464 ELECTRO-DEPOSITION OF METALS. 

planting electrotypes in copper by cliches in steel has thus far 
not been realized. 

The bath used by Klein, and still employed for this purpose, 
consists of a 10 per cent, solution of a mixture of equal parts 
of ferrous sulphate ( green vitriol) and magnesium sulphate 
(Epsom salt). The solution has a specific gravity of 1.05. To 
obtain successfully a serviceable electro from an original, 
ior instance from a copper plate, which should previously be 
silvered and coated with a thin layer of silver sulphide by 
means of sulphuretted hydrogen, the following conditions 
have to be fulfilled, according to Klein's statement: The bath 
must be kept absolutely neutral, which is effected by suspend- 
ing in it linen bags filled with magnesium carbonate, and the 
current-strength must be so regulated that absolutely no evo- 
lution of hydrogen is perceptible on the anodes. Further, the 
plates are every half hour to be taken from the bath and rinsed 
with a powerful jet of water to remove any adhering gas-bub- 
bles. Care must be taken during this process that the plates 
do not become dry, since fresh layers do not adhere well upon 
places which have become dry. 

It may here be mentioned that Lenz found a not inconsider- 
able content of hydrogen in iron deposits, and also carbonic 
acid, carbonic oxide, and nitrogen in varying quantities. How- 
ever, examinations made by Dr. Geo. Langbein established 
positively only a content of hydrogen, and it would seem that 
this hydrogen which is absorbed and tenaciously retained by 
the deposit is the cause of all the difficulties encountered in the 
production of heavy iron deposits. 

If, however, the occlusion of hydrogen is regarded as the 
cause of the mischief, ways and means to counteract it as much 
as possible may be found in the fact that iron deposited with 
greater current-density is more brittle, shows a greater tendency 
to peel off in the bath, and contains a larger quantity of hydro- 
gen than a deposit produced with slighter current-density. 

In this respect experience gained in the electrolytic refining 
of copper shows us the way in so far that for the production 



GAJLVANOPLASTY (REPRODUCTION). 465 

of heavy deposits of iron, the bath must be kept in constant, 
vigorous agitation, to remove, on the one hand, layers of fluid 
poorer in metal from the cathode, and, on the other, to force, 
by the agitation, the gas bubbles adhering to the cathode to 
escape. Further, deposition must be effected with so slight a 
current-density that no evolution of hydrogen is perceptible on 
the cathode, and a current-density of 0.25 ampere may be 
designated as the maximum per 15^ square inches, with which 
heavy deposits of iron can be produced. 

To counteract the spoiling of the deposits,. further precau- 
tionary measures are, however, necessary, especially heating 
the electrolyte and from time to time interrupting the current. 
Tn heated baths the escape of the gas is facilitated, especially 
when the electrolyte is agitated, and hence adhering gas 
bubbles cannot remain long in one place. A constantly-re- 
peated interruption of the current is of advantage and effective 
because metallic parts covered with a minimum quantity of 
hydrogen cannot be coated with a fresh deposit until the hy- 
drogen is removed by the agitation of the heated electrolyte. 
Hence the interruption of the process of deposition would give 
opportunity and time for the removal of the gas molecules be- 
fore further deposition takes place, and without a knowledge of 
the more intimate processes, Klein succeeded in effecting the 
interruption of the deposit, by taking the plates at short inter- 
vals from the bath and removing the adhering gas by a power- 
ful jet of water. 

With the present state of galvanoplasty it is not necessary to 
follow Klein's primitive method, and it will be more practical 
to provide the positive conducting rod of the bath with a con- 
trivance which mechanically effects the interruption of the cur- 
rent. Suppose upon such a metallic conducting rod is mounted 
a copper or brass wheel, which is secured to a pulley and re- 
volves around the conducting rod, and half of the periphery 
of which is insulated, and that upon the rod drags a metallic 
brush which effects the transmission of the positive current. 
Now, it will be seen that while the contact-wheel is revolving, 
30 



466 ELECTRO-DEPOSITION OF METALS. 

current is introduced only one-half the time and not during 
the other half, and that by the rapidity of revolution of the 
contact-wheel, the number of interruptions of the current can 
be varied at will. 

There can no longer be any doubt that iron electros will in 
time be produced with the same surety as copper electros, and 
that, in additions to the above-mentioned conditions, which 
have to be complied with, others will be found which may pos- 
sibly assure success in a still better manner. 

It is well known that electrolyticaily deposited iron possesses 
great hardness, and that such deposits well deserve the name 
of steel deposits, their hardness being greater than that of iron, 
and approaching that of steel. This phenomenon cannot be 
explained otherwise than by the hydrogen absorbed by the de- 
posit. Hence, it will be seen that, on the one hand, this ab- 
sorption of hydrogen has an injurious effect upon the separa- 
tion of iron, while, on the other, it imparts to the deposits the 
most valuable property of great hardness. It would seem that 
the quantities of iron first deposited upon the mould are, and 
can be, richer in hydrogen in order to impart to the printing 
surface the utmost possible hardness. However, in further 
strengthening and augmenting the deposit, our efforts must be 
directed, by the reduction of the current, to deposit strength- 
ening layers as free from hydrogen as possible. 

The question now arises, whether it is of greater advantage 
to steel a copper electro in order to increase its power of re- 
sistance, or whether it is better to produce an iron electro, and 
to strengthen its back in the acid copper bath. If the above 
expressed view that the layers of iron first deposited are richer 
in hydrogen, and therefore harder, is correct, the preference 
must be given to iron electros, because with steeled copper 
electros, the softer layers are exposed to wear, while the harder 
layers lie upon the copper plate. The reverse is the case with 
an iron electro, the first deposit, rich in hydrogen, forming the 
printing face. 

However, on the other hand, steeled copper electros have 



GALVANOPLASTY (REPRODUCTION). 467 

the advantage that, when worn, the old deposit of iron can be 
readily removed by dilute sulphuric acid, and the electros re- 
steeled, while worn iron electros have to be renewed. 

Galvanoplasty in nickel. — Though by the electro-deposition 
of nickel, electrotypes are rendered fit for printing with metallic 
colors, which attack copper, and their power of resisting wear 
is increased, the latter advantage can to the fullest extent be 
obtained only by a thick deposit. However, this always alters 
the design somewhat, especially the fine hatchings, this being 
the reason why in nickel-plating electrotypes a deposit of 
medium thickness is, as a rule, not exceeded. If a hard nickel 
surface is desired, without injury to the fine lines of the design, 
the layer of nickel has to be produced by galvanoplasty, and 
the deposit of nickel strengthened in the copper bath. 

But upon black-leaded gutta-percha or wax moulds a nickel 
deposit can only be obtained in fresh baths. The deposit, how- 
ever, is faultless only in rare cases, it generally showing holes 
in the depressions. Hence the object has to be attained in a 
round-about way, the mode of proedure being as follows : 
An impression of the original is taken in gutta-percha or wax, 
and from this impression a positive cliche in copper is made. 
The latter is then silvered, the silvering iodized as previously 
described, and a negative in copper is then prepared from this 
positive. The negative is again silvered, iodized, and then 
brought into a nickel bath, where it receives a deposit of the 
thickness of stout writing paper. It is then rinsed in water, and 
the deposit immediately strengthened in the acid copper bath. 
For the rest, it is treated like ordinary copper deposits. Nickel 
electrotypes thus made are almost indestructible. 

Galvanoplasty in silver and gold. — The preparation of re- 
productions in silver and gold also presents many difficulties. 
While copper is separable in a compact state from its sulphate 
solution, silver and gold have to be reduced from their double 
salt solutions — potassium silver cyanide and potassium gold 
cyanide. However, these alkaline solutions attack moulds of 
fatty substances, such as wax and stearine, consequently also, 



468 ELECTRO-DEPOSITION OF METALS. 

plaster-of-Paris moulds impregnated with these substances, as 
well as gutta-percha and gelatine. Hence, only metallic moulds 
can be advantageously used, except the end is to be attained 
in a round-about way ; that is, by first coating the mould with a 
thin film of copper, strengthening this in the silver or gold 
bath, and fially dissolving the film of copper with dilute nitric 
acid. 

The double salt solutions mentioned above require a well- 
conducting surface such as cannot be readily prepared by 
black-leading, a further reason why metallic moulds are to be 
preferred. The simplest way for the galvanoplastic repro- 
duction in gold or silver of surfaces not in high relief or under- 
cut, is to cover the object with lead, silver, or gold foil, and 
pressing softened gutta-percha upon it; the foil yields to the 
pressure without tearing, and adheres to the gutta-percha so 
firmly that it can be readily separated together with it. Gal- 
vanoplastic reproductions in the noble metals are so seldom 
made in practice that it is not necessary to give further de- 
tails. The composition of the baths generally used is as 
follows : 

Bath for galvanoplasty in silver. — Fine silver (in the form 
of silver cyanide or silver chloride) I ^ ozs., 98 per cent, 
potassium cyanide 5^ ozs., water 1 quart. 

Bath for galvanoplasty in gold. — Fine gold (in the form of 
neutral chloride of gold) 1 oz., potassium cyanide 3^ ozs., 
water 1 quart. 



CHAPTER XV. 

COLORING, PATINIZING, OXIDIZING, ETC., OF METALS. — 
LACQUERING. 

Though, strictly speaking, these operations do not form a 
part of a work on the electro-deposition of metals, they re- 
quire to be mentioned, since the operator is frequently forced 
to make use of one or the other method in order to furnish 
basis-metals or electro-deposits in certain shades of colors 
ordered. 

By patina is understood the beautiful green color antique 
statues and other art-works of bronze acquire by long exposure 
to the action of the oxygen, carbonic acid, and moisture of the 
air, whereby a thin layer of copper carbonate is formed upon 
them. It has been sought to accelerate by chemical means 
the formation of the patina thus slowly produced by the in- 
fluence of time, and the term patinizing has been applied to 
this artificial production of colors. Without drawing a strict 
line as to which processes have to be considered as coloring, 
and which as patinizing, the most approved methods for 
changing the color of the metals or of the deposits will be 
given. 

i. Coloring of copper. — All shades from the pale-red of cop- 
per to a dark chestnut-brown can be obtained by superficial 
oxidation of the copper. For small objects it suffices to heat 
them uniformly over an alcohol flame. With larger objects a 
more uniform result is obtained by heating them in oxidizing 
fluids or brushing them over with an oxidizing paste, the best 
results being obtained with a paste prepared, according to the 
darker or lighter shades desired, from 2 parts of ferric oxide 
and I part of black-lead, or t part each of ferric oxide and 

(469) 



470 ELECTRO-DEPOSITION OF METALS. 

black-lead, with alcohol or water. Apply the paste as uni- 
formly as possible with a brush, and place the object in a warm 
place (oven or drying chamber). The darker the color is to 
be the higher the temperature must be, and the longer it must 
act upon the object. When sufficiently heated the dry powder 
is removed by brushing with a soft brush, and the manipulation 
repeated if the object does not show a sufficiently dark tone. 
Finally the object is rubbed with a soft linen rag moistened 
with alcohol, or brushed with a soft brush and a few drops of 
alcohol until completely dry, and then with a brush previously 
rubbed upon pure wax. The more or less dark shade pro- 
duced in this manner is very warm, and resists the action of 
the air. 

Brown color upon copper is obtained by applying to the 
thoroughly cleansed surface of the object a paste of verdigris 
3 parts, ferric oxide 3, sal ammoniac 1, and sufficient vinegar, 
and heating until the applied mixture turns black. The ob- 
ject is then washed and dried. By the addition of some blue 
vitriol the color may be darkened to chestnut-brown. 

In England a brown layer of cuprous oxide upon copper 
articles is produced as follows : After polishing the articles with 
pumice powder apply with a brush a paste of 4 parts of verdi- 
gris, 4 parts of colcothar (ferric oxide), 1 part of finely rasped 
horn shavings and a small quantity of vinegar. Dry, heat over 
a coal fire, wash, and smooth with the polishing stone. 

A brown color is also obtained by brushing to dryness with a 
hot solution of 1 part of potassium nitrate, 1 of common salt, 
2 of ammonium chloride, and 1 of liquid ammonia in 95 of 
vinegar. A warmer tone is, however, produced by the method 
introduced in the Paris Mint, which is as follows : Powder and 
mix intimately equal parts of verdigris and sal ammoniac. 
Take a heaping tablespoonful of this mixture and boil it with 
water in a copper kettle for about twenty minutes and then 
pour off the clear fluid. To give copper objects a bronze-like 
color with this fluid, pour part of it into a copper pan; place 
the objects separately in it upon pieces of wood or glass, so 



COLORING, PATINIZING, OXIDIZING, ETC. 47 1 

that they do not touch each other, or come in contact with the 
copper pan, and then boil them in the liquid for a quarter of 
an hour. Then take the objects from the solution, rub them 
dry with a linen cloth, and brush them with a waxed brush. 

A red-brown color on copper is produced in China by the 
application of a paste of verdigris 2 parts, cinnabar 2, sal am- 
moniac 5, and alum 5, with sufficient vinegar, heating over a 
coal fire, washing, and repeating the process. 

According to Manduit, copper and coppered articles may 
be bronzed by brushing with a mixture of castor oil 20 parts, 
alcohol 80, soft soap 40, and water 40. This mixture produces 
tones from bronze Barbedienne to antique green patina, accord- 
ing to the duration of the action. After 24 hours the article 
treated shows a beautiful bronze, but when the mixture is 
allowed to act for a greater length of time the tone is changed 
and several different shades of great beauty are obtained. After 
rinsing, dry in hot saw- dust, and lacquer with colorless spirit 
lacquer. 

Copper is colored blue-black by dipping the object in a hot 
solution of 1 1 y^ drachms of liver of sulphur in 1 quart of water, 
moving it constantly. Blue-gray shades are obtained with 
more dilute solutions. It is difficult to give definite directions 
as to the length of time the solution should be allowed to act, 
since this depends on its temperature and concentration. With 
some experience the correct treatment, however, will soon be 
learned. 

The so-called cuivre fume is produced by coloring the copper 
•or coppered objects blue black with solution of liver of sulphur, 
then rinsing, and finally scratch-brushing them, whereby the 
shade becomes somewhat lighter. From raised portions which 
are not to be dark, but are to show the color of copper, the 
coloration is removed by polishing upon a felt wheel or bob. 

Black color upon copper is produced by a heated pickle of 2 
parts of arsenious acid, 4 of concentrated muriatic acid, 1 of 
sulphuric acid of 66° Be., and 24 of water. 

Matt-black on copper.— -Brush the object over with a solution 



472 ELECTRO-DEPOSITION OF METALS. 

of I part of platinum chloride in 5 of water, or dip it in the 
solution. A similar result is obtained by dipping the copper 
object in a solution of nitrate of copper or of manganese, and 
drying over a coal fire. These manipulations are to be repeated 
until the formation of a uniform matt-black. 

A solution recommended for obtaining a deep black color on 
copper and its alloys is composed as follows : Copper nitrate 
100 parts, water 100 parts. The copper nitrate is dissolved in 
the water, and the article, if large, is painted with it; if small, 
it may be immersed in the solution. It is then heated over a 
clear coal fire and lightly rubbed. The article is next placed 
in, or painted, with a solution of the following composition r 
Potassium sulphide 10 parts, water 100, hydrochloric acid 5. 

More uniform results, however, are obtained by using a 
solution about three times more dilute than the above, viz. : 
Copper nitrate 100 parts, water 300. Small work can be much 
more conveniently treated by immersion in the solution, and 
after draining off, or shaking ofT, the excess of the solution, 
heating the work on a hot plate until the copper salt is decom- 
posed into the black copper oxide. It would be difficult to 
heat large articles on a hot plate, but a closed muffle furnace 
should give better results than an open coal fire. In any case 
the heating process should not be continued longer than neces- 
sary to produce the change mentioned above. 

Imitation of genuine patina. — Repeatedly brush the objects 
with solution of sal ammoniac in vinegar. The action of the 
solution is accelerated by the addition of verdigris. A 
solution of 9 drachms of sal ammoniac and 2]/^ drachms of 
potassium binoxalate in 1 quart of vinegar acts still better. 
When the first coating is dry, wash the object, and repeat the 
manipulations, drying and washing after each application, until 
a green patina is formed. It is best to bring the articles after 
being brushed over with the solution into a hermetically closed 
box, upon the bottom of which a few shallow dishes containing 
very dilute sulphuric or acetic acid and a few pieces of marble 
are placed. Carbonic acid being thereby evolved, and the air 



COLORING, PATINIZING, OXIDIZING, ETC. . 473 

in the box being kept sufficiently moist by the evaporation of 
water, the conditions required for the formation of genuine 
patina are thus filled. If the patina is to show a more bluish 
tone, biush the objects with a solution of 4% ozs. of ammonium 
carbonate and 1 yi ozs. of sal ammoniac in 1 quart of water, to 
which a small quantity of gum tragacanth may be added. 

To produce a steel-gray color upon copper immerse the clean 
and pickled objects in a heated solution of chloride of antimony 
in hydrochloric acid. By using a strong electric current the 
objects may also be coated with a steel-gray deposit of arsenic 
in a heated arsenic bath. 

For coloring copper dark steel-gray, a pickle consisting of 1 
quart of hydrochloric acid, 0.125 quart of nitric acid, 1 ^ ozs. 
of arsenious acid, and a like quantity of iron filings is recom- 
mended. 

Various colors upon massive copper. — First draw the object 
through a pickle composed of sulphuric acid 60 parts, hydro- 
chloric acid 24.5, and lampblack 15.5; or of nitric acid 100 
parts, hydrochloric acid i}4 f and lampblack }(. Then dissolve 
in a quart of water \]/ 2 ozs. of sodium hyposulphite, and in 
another quart of water 14%! drachms of blue vitriol, 5^ 
drachms of crystallized verdigris, and 7^ grains of sodium 
arsenate. Mix equal volumes of the two solutions, but no 
more than is actually necessary for the work in hand, and heat 
to between 167 and 176 F. By dipping articles of copper, 
brass or nickel in the hot solution they become immediately 
colored with the colors mentioned below, one color passing 
within a few seconds into the other, and for this reason the effect 
must be constantly controlled by frequently taking the objects 
from the bath. The colors successively formed are as follows : 

Upon copper : Upon brass : Upon nickel : 

Orange, Golden-yellow, Yellow, 

Terra-cotta, Lemon color, Blue, 

Red (pale), Orange, Iridescent. 

Blood-red, Terra-cotta, 

Iridescent. Olive-green. 



474 ELECTRO-DEPOSITION OF METALS. 

Some of these colors not being very durable, have to be 
protected by a coat of lacquer or paraffine. It is further 
necessary to diligently move the objects, so that all portions 
acquire the same color. The bath decomposes rapidly, and 
hence only sufficient for 2 or 3 hours' use should be mixed at 
one time. 

2. Coloring of brass and bronzes. — Most of the directions 
given for coloring copper are also available for brass and 
bronzes, especially those for the production of the green patina, 
and the oxidized tones by a mixture of ferric oxide and black- 
lead. 

Many colorations on brass, however, are effected only with 
difficulty, and are partially or entirely unsuccessful, as, for in- 
stance, coloring black with liver of sulphur. As a pickle for 
the production of a 

Lustrous black on brass, the following solution may be used : 
Dissolve freshly precipitated carbonate of copper, while still 
moist, in strong liquid ammonia, using sufficient of the copper 
salt so that a small excess remains undissolved, or, in other 
words, that the ammonia is saturated with copper. The car- 
bonate of copper is prepared by mixing hot solutions of equal 
parts of blue vitriol and of soda, filtering off, and washing the 
precipitate. 

Dilute the solution of the copper salt in ammonia with one- 
fourth its volume of water, add 3 1 to 46 grains of graphite and 
heat to between 95 and 104 F. 

According to experiments in the laboratory of the Physikal- 
isch-Technischen Reichsanstalt, the following proportions have 
proved very effective: Copper carbonate 3^ ozs., spirits of 
sal ammoniac 26^ ozs., and an addition of 5*^ ozs. of water. 
Place the clean and pickled articles in this pickle until they show 
a full black tone, then rinse in water, immerse in hot water, and 
dry in sawdust. The solution soon spoils, and hence no more 
than required for immediate use should be prepared. 

For black pickling in the hot way, a solution of 21 ozs. of 
copper nitrate in 7 ozs. of water mixed with a solution of 3^ 
grains of silver nitrate in y^ oz. of water, is recommended. 



COLORING, PATINIZING, OXIDIZING, ETC. 475 

Another method of coloring brass black has been given 
under " Deposition of Arsenic." 

Urquhart states that clean brass and copper may be covered 
with a firmly adherent black coating by placing them very near 
to the flames of burning straw. The coating will not rub off, 
and may be polished with a soft cloth. 

Steel-gray on brass is obtained by the use of a mixture of 1 lb. 
of strong hydrochloric acid with 1 pint of water, to which are 
added 5*^ ozs. of iron filings and a like quantity of pulverized 
antimony sulphide. 

Hydrochloric acid compounded with arsenious acid is also 
recommended for this purpose. The mixture is brought into 
a lead vessel, and the objects dipped in it should come in con- 
tact with the lead of the vessel, or be wrapped around with a 
strip of lead. 

A gray color with a bluish tint upon brass is produced with 
solution of antimonious chloride (butter of antimony), while a 
pure steel-gray color is obtained with a hot solution of arsenious 
chloride with a little water. 

A pale gold color on brass is obtained in the following bath : 
Dissolve in 90 parts by weight of water, 3.6 parts by weight of 
caustic soda and the same quantity of milk sugar. Boil the 
solution y^ hour. Then add a solution of blue vitriol 3.6 
parts by weight in 10 of hot water, and use the bath at a tem- 
perature of 176 F. 

Straw color, to brown, through golden yellonn, and tombac color 
vn brass may be obtained with solution of carbonate of copper 
in caustic soda lye. Dissolve 5.25 ozs. of caustic soda in 1 
quart of water, and add 1 ^ ozs. of carbonate of copper. By 
using the solution cold, a dark golden-yellow is first formed, 
which finally passes through pale brown into dark brown with a 
green lustre. Coloration is more rapidly effected by using the 
solution hot. 

A color resembling gold on brass is, according to Dr. Kayser, 
obtained as follows : Dissolve S}4 drachms of sodium hyposul- 
phite in 1 7 drachms of water, and add 5 .64 drachms of solution of 



47^ ELECTRO-DEPOSITION OF METALS. 

antimonious chloride (butter of antimony ) . Heat the mixture to 
boiling for some time, then filter off the red precipitate formed,, 
and after washing it several times upon the filter with vinegar, 
suspend it in 2 or 3 quarts of hot water; then heat and add con- 
centrated soda lye until solution is complete. In this hot 
solution dip the clean and pickled brass objects, removing them 
frequently to see whether they have acquired the desired color- 
ation. By remaining too long in the»bath, the articles become 
gray. 

Brown color, called bronze Barb edienne, on brass. — This beau- 
tiful color may be produced as follows : Dissolve by vigorous 
shaking in a bottle, freshly prepared arsenious sulphide in spirit 
of sal ammoniac, and compound the solution with antimonious 
sulphide (butter of antimony) until a slight permanent turbidity 
shows itself, and the fluid has acquired a deep yellow color. Heat 
the solution to 95 F., and suspend the brass objects in it. They 
become at first golden-yellow and then brown, but as they come 
from the bath with a dark dirty tone, they have to be several times 
scratch-brushed to bring out the color. If, after using it several 
times, the solution fails to work satisfactorily, add some anti- 
monious sulphide. The solution decomposes rapidly, and 
should be prepared fresh every time it is to be used. 

By this method only massive brass objects can be colored 
brown. To brassed zinc and iron the solution imparts brown 
black tones, which, however, are also quite beautiful. 

Upon massive brass, as well as upon brassed zinc and iron 
objects, bronze Barbedienne may be produced as follows : Mix 
3 parts of red sulphide of antimony (stibium sulfur atum aura?i- 
tianum) with 1 part of finely pulverized bloodstone, and tritu- 
rate the mixture with ammonium sulphide to a not too thickly- 
fluid pigment. Apply this pigment to the objects with a 
brush, and, after allowing to dry in a drying chamber, remove 
the powder by brushing with a soft brush. 

In Paris, bronze articles are colored dead-yellow or clay-yel- 
low to dark brown by first brushing the pickled and thoroughly 
rinsed objects with dilute ammonium sulphide, and, after dry- 



COLORING, PATINIZING, OXIDIZING, ETC. 477 

ingj removing the coating of separated sulphur by brushing. 
Dilute solution of sulphide of arsenic in ammonia is then ap- 
plied, the result being a color resembling mosaic gold. The 
more frequently the arsenic solution is applied, the browner the 
color becomes. By substituting for the arsenic solution one of 
sulphide of antimony in ammonia or ammonium sulphide, color- 
ations of a more reddish tone are obtained. 

Smoke-bronze. — Bronzing with smoke is sometimes resorted 
to in order to give the metal an ancient appearance. This is 
effected by exposing the work to the smoke of a fire for some 
days, when it receives a firm coating of a dark color. The 
articles are generally suspended over the smoky fire of a 
furnace by means of brass wire. When the furnace is suffi- 
ciently heated the smoke is maintained by burning hay and 
other substances which produce copious smoke with the coal. 
When the right tint is attained the articles are removed from 
the furnace and allowed to cool without touching them with 
the hands. The hotter the articles have been made the darker 
will be the color. If the articles which have been smoked have 
been previously coated with a green bronze, then it is well to 
finish with a waxed brush. 

A dark red brown color upon brass is produced by suspend- 
ing the articles, previously thoroughly freed from grease, in a 
solution of equal parts of potassium lead oxide and red prus- 
siate of potash heated to 122 F. The articles are allowed to 
remain in the solution until they have acquired a sufficiently 
dark color. 

For coloring brass articles en masse brown by boiling, the 
following solution is recommended : Water 1 quart, potassium 
chromate \]/ 2 ozs., nickel sulphate lyi ozs., potassium perman- 
ganate jy grammes. 

Solution of blue vitriol and potassium permanganate serves 
the same purpose. However, after boiling, the articles must 
not be scratch brushed, but after drying rubbed with vaseline. 

Violet- and corn-flower bine upon brass may be produced as 
iollows : Dissolve in 1 quart of water 4^ ozs. of sodium hypo- 



47 8 ELECTRO-DEPOSITION OF METALS. 

sulphite, and in another quart of water I oz. 3^ drachms of 
crystallized sugar of lead, and mix the solutions. Heat the 
mixture to 176 F., and then immerse the cleansed and pickled 
articles, moving them constantly. First a gold-yellow colora- 
tion appears, which, however, soon passes into violet and blue, 
and if the bath be allowed to act further, into green. The 
action is based upon the fact that in an excess of hyposulphite 
of soda, solution of hyposulphite of lead is formed, which de- 
composes slowly and separates sulphide of lead, which precipi- 
tates upon the brass objects and, according to the thickness of 
the deposit, produces the various lustrous colors. 

Upon the same action is based the spurious gilding of small 
silvered brass and tombac articles. Though this process has 
been known for many years, Joseph Dittrich obtained a German 
patent for it. He uses for 6^ lbs. of water, ioj^ ozs. of sodium 
hyposulphite, and 3^ ozs. of lead acetate (sugar of lead). 

Similar lustrous colors are obtained by dissolving 2.1 1 ozs. 
of pulverized tartar in 1 quart of water, and 1 oz. of chloride of 
tin in y 2 pint of water, mixing the solution, heating, and pour- 
ing the clear mixture into a solution of 6.34 ozs. of sodium 
hyposulphite in 1 pint of water. Heat this mixture to 176 F., 
and immerse the pickled brass objects. 

Ebermayer s experiments in coloring brass. — Below the results 
of Ebermayer's experiments are given. In testing the direc- 
tions, the same results as those claimed by Ebermayer were not 
always obtained ; and variations are given in parentheses. 

I. Blue vitriol 8 parts by weight, crystallized sal ammoniac 
2, water 100, give by boiling a greenish color. (The color is 
olive-green, and useful for many purposes. The coloration, 
however, succeeds only upon massive brass, but not upon 
brassed zinc.) 

II. Potassium chlorate 10 parts by weight, blue vitriol 10, 
water 1000, give by boiling a brown-orange to cinnamon-brown 
color. (Only a yellow-orange color could be obtained.) 

III. By dissolving 8 parts by weight of blue vitriol in 1000 
of water, and adding 100 of caustic soda until a precipitate is 



COLORING, PATINIZING, OXIDIZING, ETC. ' 479 

formed, and boiling the objects in the solution a gray-bfown t 
color is obtained, which can be made darker by the addition of 
colcothar. (Stains are readily formed. Brassed zinc acquires 
a pleasant pale-brown.) 

IV. With 50 parts by weight of caustic soda, 50 of sulphide 
of antimony, and 500 of water, a pa\e fig-brown color is pro- 
duced. (Fig-brown could not be obtained, the shade being 
rather dark olive- green. ) 

V. By boiling 400 parts by weight of water, 25 of sulphide 
of antimony and 60 of calcined soda, and filtering the hot solu- 
tion, mineral kermes is precipitated. By taking of this 5 parts 
by weight and heating with 5 of tartar, 400 of water, and 10 of 
sodium hyposulphite, a beautiful steel-gray is obtained. (The 
result is tolerably sure and good.) 

VI. Water 400 parts by weight, potassium chlorate 20, 
nickel sulphide 10, give after boiling for some time a brown 
color, which, however, is not formed if the sheet has been 
pickled. (The brown color obtained is not very pronounced. ) 

VII. Water 250 parts by weight, potassium chlorate 5, car- 
bonate of nickel 2, and sulphate of ammonium and nickel 5, 
give after boiling for some time a brown-yellow color, playing 
into a magnificent red. (The results obtained were only in- 
different.) 

VIII. Water 250 parts by weight, potassium chlorate 5, and 
sulphate of nickel and ammonium 10, give a beautiful dark 
brown. (Upon massive brass a good dark-brown is obtained. 
The formula, however, is not available for brassed zinc.) 

3. Coloring zinc. — The results obtained by coloring zinc 
directly according to existing directions cannot be relied on, 
and it is, therefore, recommended to first copper the zinc and 
then color the coppering. Experiments in coloring zinc black 
with alcoholic solution of chloride of antimony according to 
Dullas's process gave no useful results. Puscher's method is 
better. According to it the objects are dipped in a boiling 
solution of 5.64 ozs. of pure green vitriol and 3.17 ozs. of sal 
ammoniac in 2]/ 2 quarts of water. The loose black precipitate 



480 ELECTRO-DEPOSITION OF METALS. 

deposited upon the objects is removed by brushing, the object 
again dipped in the hot solution, and then held over a coal fire 
until the sal ammoniac evaporates. By repeating the operation 
three or four times a firmly-adhering black coating is formed. 
To color zinc black with nitrate of manganese, as proposed by 
Neumann, is a tedious operation, it requiring to be repeated 
seven or eight times. It is done by dipping the object in a 
solution of nitrate of manganese and heating over a coal fire, 
the manipulations being repeated until a uniform dead-black is 
obtained. 

Gray, yellow, brown to black colors upon zinc are obtained by 
bringing the articles into a bath which contains 6 to 8 quarts of 
water, 3^ ozs. of nickel ammonium sulphate, 3^ ozs. of blue 
vitriol and 3^ ozs. of potassium chlorate. The bath is to be 
heated to 140 F. By increasing the content of blue vitriol a 
dark color is obtained, and a lighter one with the use of a 
larger proportion of nickel salt. The correct proportions for 
the determined shades will soon be learned by practice. 
When colored, the articles are thoroughly rinsed, dried, with- 
out rubbing, in warm sawdust, and finally rubbed with a flannel 
rag moistened with linseed oil, whereby they acquire deep 
lustre, and the coating becomes more durable. 

By suspending zinc in a nickel bath slightly acidulated with 
sulphuric acid, a firmly adhering blue-black coating is, after 
some time, formed without the use of a current. This coating 
is useful for many purposes. A similar result is obtained by 
immersing the zinc objects in a solution of 2.1 1 ozs. of the 
double sulphate of nickel and ammonium and a like quantity 
of sal ammoniac in I quart of water. The articles become first 
dark yellow, then, successively, brown, purple-violet, and indigo 
blue, and stand slight scratch-brushing and polishing. 

A gray coating on zinc is obtained by a deposit of arsenic in 
a heated bath composed of 2.82 ozs. of arsenious acid, 8.46 
drachms of sodium pyrophosphate and 1 ^ drachms of 98 per 
cent, potassium cyanide and 1 quart of water. A strong cur- 
rent should be used so that a vigorous evolution of hydrogen 



COLORING, PATINIZING, OXIDIZING, ETC. 48 1 

is perceptible. Platinum sheets or carbon plates are used as 
anodes. 

A sort of bronzing on zinc is obtained by rubbing it with a 
paste of pipe-clay to which has been added a solution of 1 part 
by weight of crystallized verdigris, I of tartar, and 2 of crys- 
tallized soda. 

Kletzinski states that a solution of molybdic acid, or ammo- 
nium molybdate, in nitric acid, made very dilute, furnishes a 
good liquid for producing a brown patina on cast zinc. The 
object assumes iridescent colors on immersion, which he con- 
siders to be due to molybdenum oxide. The following pro- 
portions were tried, with the results given below: Ammonium 
molybdate 1.550 grains, ammonia 2.325 grains, water 1 pint. 

Zinc acquired a beautiful iridescent appearance after a few 
moments' immersion in the solution. On continuing the pro- 
cess, the iridescent colors were succeeded by a light yellowish- 
brown color, and this, on warming the solution, was followed 
by a slaty-black, which was more opaque than any of the pre- 
ceding colors. 

Brass and tin are unaffected when immersed alone, but tin 
when placed in contact with zinc assumes a beautiful dark violet 
color, which is firmly adherent to the metal. Iron in contact 
with tin is simply stained. 

Red-brown shades on zinc. — Rub with solution of chloride of 
copper in liquid ammonia. 

Yellow brown shades on zinc. — Rub with solution of chloride 
of copper in vinegar. 

4. Coloring of iron. — The browning of gun-barrels is effected 
by the application of a mixture of equal parts of butter of anti- 
mony and olive oil. Allow the mixture to act for 12 to 14 
hours, then remove the excess with a woolen rag and repeat 
the application. When the second application has acted for 12 
to 24 hours, the iron or steel will be coated with a bronze- 
colored layer of ferric oxide with antimony, which resists the 
action of the air, and may be made lustrous by brushing with a 
waxed brush. 
31 



482 ELECTRO -DEPOSITION OF METALS. 

A patina which protects metals — iron, zinc, tin, etc. — from 
rust, is, according to Haswell, obtained as follows : The arti- 
cle, previously freed from grease and pickled, is suspended as 
negative electrode in a solution of 1 5 x / 2 grains of ammonium 
molybdate and y^ oz. of ammonium nitrate in 1 quart of water. 
A weak current should be used — 0.2 to 0.3 ampere per 153^ 
square inches. 

To protect gun barrels and other articles of iron and steel 
from rust, they are, according to Haswell, suspended as anodes 
in a bath consisting of a solution of lead nitrate and sodium 
nitrate, into which manganous oxide has been stirred. 

A lustrous black on iron is obtained by the application of 
solution of sulphur in spirits of turpentine prepared by boiling 
upon the water bath. After the evaporation of the spirits of 
turpentine a thin layer of sulphur remains upon the iron, which 
on heating the article immediately combines with the metal. 

A lustrous black is also obtained by freeing the iron articles 
from grease, pickling, and after drying, coating with sulphur 
balsam,* and burning in at a dark-red heat. If pickling is 
omitted, coating with sulphur balsam and burning-in must be 
twice or three times repeated. 

The same effect is produced by applying a mixture of three 
parts flower of sulphur, and one part graphite with turpentine 
and heating in the muffle. 

According to Meritens a bright black color can be obtained 
on iron by making it the anode in distilled water, kept at 15 8° 
F., and using an iron plate as a cathode. The method was 
tested as follows : A piece of bright sheet pen-steel was placed 
in distilled water and made the anode by connecting with the 
positive pole of a plating dynamo, and a similar sheet was con- 
nected with the negative pole to form the cathode. An electro- 
motive force of 8 volts was employed. After some time a dark 
stain was produced, but it lacked uniformity. The experi- 
ment was repeated with larger plates, when a good blue-black 

* Sulphur dissolved in linseed oil. 



COLORING, PATINIZING, OXIDIZING, ETC. 483 

color was obtained on the anode in half an hour. On drying 
out in sawdust the color appeared less dense, and inclined to a 
dark straw tint. The back of the plate was also colored, but 
not regularly. The face of the cathode was discolored with a 
grayish stain on the side opposite to the anode, but on the 
other side the appearance was almost identical with the back of 
the anode. The water became of a yellowish color. 

Fresh distilled water was then boiled for a long time so as 
to expel all trace of the oxygen absorbed from the atmosphere, 
and the experiment repeated as in the former cases. No per- 
ceptible change took place after the connection had been made 
with the dynamo for a quarter of an hour. After the interval 
of one hour a slight darkening occurred, but the effect was 
much less than that produced in five minutes in aerated water. 

The action of the liquid in coloring the steel is evidently one 
of oxidation, due to the dissolved oxygen, which becomes 
more chemically active under the influence of the electric con- 
dition, and gradually unites with the iron. 

The dead black coating on clock cases of iron and steel is 
not produced by the galvanic process. For this purpose it is 
recommended to brush the slightly heated metallic parts with 
a solution of 70 parts copper nitrate in 30 parts spirits of wine 
and then heat them. A black coating of copper oxide is 
formed, which after cooling is rubbed off, and an adhering gray 
layer remains behind. By repeating the operation pure black 
tones are obtained. 

According to Bottger a durable blue on iron and steel may 
be obtained by dipping the article in a y 2 per cent, solution of 
red prussiate of potash mixed with an equal volume of a j£ 
per cent, ferric chloride solution. 

A brown-black coating with bronze lustre on iron is obtained 
by heating the bright iron objects and brushing them over 
with concentrated solution of potassium bichromate. When 
dry, heat them over a charcoal fire, and wash until the water 
running off shows no longer a yellow color. Repeat the opera- 
tion twice or three times. A similar coating is obtained by 



484 ELECTRO-DEPOSITION OF METALS. 

heating the iron objects with a solution of 10 parts by weight 
of green vitriol and 1 part of sal ammoniac in water. 

To give iron a silvery appearance with high lustre. — Scour 
the polished and pickled iron objects with a solution prepared 
as follows: Heat moderately 1 y 2 ozs. of chloride of antimony, 
0.35 oz. of pulverized arsenious acid, 2.82 ozs. of elutriated 
bloodstone with 1 quart of 90 per cent, alcohol upon a water 
bath for half an hour. Partial solution takes place. Dip into 
this fluid a tuft of cotton and go over the iron portions, using 
slight pressure. A thin film of arsenic and antimony is thereby 
deposited, which is the more lustrous the more carefully the 
iron has previously been polished. 

5. Coloring of tin. — A bronze- like patina on tin may be ob- 
tained by brushing the object with a solution of 1 ^ ozs. of 
blue vitriol and a like quantity of green vitriol in 1 quart of 
water, and moistening, when dry, with a solution of 3^ ozs. of 
verdigris in 10^ ozs. of vinegar. When dry, polish the object 
with a soft waxed brush and some ferric oxide. The coating 
thus obtained being not very durable, must be protected by a 
coating of lacquer. 

Durable and very warm sepia-brown tone upon tin and its 
alloys. — Brush the object over with a solution of 1 part of plat- 
inum chloride in 10 of water, allow the coating to dry, then 
rinse in water, and, after again drying, brush with a soft brush 
until the desired brown lustre appears. 

A dark coloration is also obtained with ferric chloride 
solution. 

6. Coloring of silver — See " Deposition of Silver," p. 331. 

Lacquering. 

In the electro-plating industry recourse is frequently had to 
lacquering in order to make the deposits more resistant against 
atmospheric influences, or to protect artificially prepared colors, 
patinas, etc. Thin, colorless shellac solution, which does not 
affect the color of the deposit or of the patinizing, is, as a rule, 
employed, while in some cases colored lacquers are used to 



COLORING, PATINIZING, OXIDIZING, ETC. 485 

heighten the tone of the deposit, as, for instance, gold lacquer 
for brass. 

The lacquer is applied by means of a fine flat fitch-brush, 
the object having previously been heated hand-warm. After 
lacquering, the object is dried in an oven at a temperature of 
between 140 and 15 8° F., whereby small irregularities are ad- 
justed, and the layer of lacquer becomes transparent, clear, 
and lustrous. 

Electro-plated articles which are to be lacquered must be 
thoroughly rinsed and dried to remove adhering plating solu- 
tion from the pores, otherwise ugly stains will form under the 
coat of lacquer. 

If it becomes necessary to thin a spirit lacquer, only absolute 
alcohol, i. e.y alcohol free from water, should be used for the 
purpose, since alcohol containing water renders the coat of 
lacquer muddy and dull. 

A few words may here be said in regard to the processes by 
which those beautiful effects are obtained which imitate so 
completely the appearance, freshness and rich tones of real 
gilding. In general, gold varnish is applied only upon copper 
and its more or less yellow alloys. 

Gold varnishers operate as follows : After the objects have 
been perfectly cleansed, scratch-brushed, and burnished, if 
necessary, they are completely dried in hot sawdust and wiped 
clean with a fine cloth. A light coat of varnish is then applied 
with a fitch-pencil, and all excess of varnish removed or leveled 
with another flat brush of badger-hair or bristles. The two 
brushes are kept together in the same hand, the varnish brush 
between the thumb and first two fingers, while the flat one 
(without a handle) is held between the other fingers and the 
palm of the hand. In this manner there is no interval in the 
use of the two brushes. The varnish is kept in a jelly-pot or 
other similar vessels, across the top of which a string has been 
stretched. This string is intended for removing by wiping the 
excess of varnish taken up by the brush or pencil. The var- 
nish which covers the burnished parts of the object may be re- 



486 ELECTRO-DEPOSITION OF METALS. 

moved with a clean rag moistened with alcohol and wrapped 
round the finger. Another dry cloth finishes the drying. 
Sometimes the burnished parts are also varnished, but the opera- 
tion is very difficult when their surface is considerable. Round- 
ware, polished or burnished, may be varnished in the lathe. 

After the varnish has been applied as uniformly as possible, 
the objects are put in a drying stove heated to between 140 
and 1 75° F. The alcohol or essential oils of the varnish are 
rapidly volatilized, while the resins or gums melt and cover the 
objects with a glassy lustre. The heat must be sufficient to 
melt these gums, but low enough to avoid burning them. 
When the operation has been well performed, the pieces pre- 
sent a beautiful and uniform golden appearance, with no disfig- 
uring red patches, which latter indicate an unequal thickness of 
varnish. 

Varnishers have always at their disposal four varnishes of 
different shades — red gold, orange-yellow gold, green gold, and 
colorless varnish for mixture. This last is employed for dilut- 
ing the first three and diminishing the depth of their colors. 
Each of these various varnishes gives to copper the gold color 
peculiar to it, and, when mixed, intermediary shades. It often 
happens that the various parts of a large piece are different in 
composition and color, and the varnisher is obliged to impart 
the same shade of gold all over by skilful combinations of var- 
nishes. He thus succeeds in giving the same gold color to 
half-red copper and to alloys of yellow and green brass. 

But a small quantity of varnish is poured into the varnish 
pot at one time, to prevent it from thickening by evaporation, 
and after the operation the residue is poured back into the 
flask from which it was taken and kept well stoppered. The 
brushes and pencils must be often washed in alcohol, which 
may afterwards be used for diluting thick varnishes. 

These varnishes are made by dissolving various resinous sub- 
stances, like sandarac, benzoin, dragon's-blood, elemi, gamboge, 
etc., and tinctorial matters, such as saffron, annotto, alkanet, 
etc., in a mixture of alcohol with essence of lavender or of 



COLORING, PATINIZING, OXIDIZING, ETC. 487 

spikenard. All qualities of varnish are to be found, but the 
more expensive are often the more economical. 

To remove the varnish from an imperfectly varnished object 
or from an old one, it is immersed in alcohol or concentrated 
sulphuric acid, or, better still, in a boiling solution of caustic lye. 
The varnishing is then begun anew. 

Cellulose lacquers and varnishes. — Under the name of zapon 
a dip-lacquer has been introduced in commerce. It represents 
a clear, almost colorless fluid of the consistency of collodion, 
and smells something like fruit ether. According to G. Buch- 
ner, it consists essentially of a solution of cellulose in a mixture 
of amyl acetate and acetone. Of the last two bodies, the 
" thinning fluid," which accompanies the preparation, also con- 
sists. This lacquer can be highly recommended, its superiority 
being due to the favorable properties of the cellulose. The 
transparent, colorless coat obtained with zapon can be bent 
with the metallic sheet to which it has been applied without 
cracking. It is so hard that it can scarcely be scratched with 
the finger-nail, shows no trace of stickiness, and it is perfectly 
homogeneous even on the edges. This favorable behavior is 
very likely due to the slow evaporation of the solvent, and the 
fact that the lacquer quickly forms a thickish, tenacious layer, 
which, though moved with difficulty, is not entirely immobile. 
Another advantage of zapon — especially as regards metallic 
objects — is that the coating, in consequence of its physical 
constitution, preserves the character of the basis. In ac- 
cordance with the nature of cellulose, the coating is not sen- 
sibly affected by ordinary differences in temperature, and does 
not become dull and non-transparent, as is the case with resins, 
in consequence of the loss of molecular coherence. It can be 
washed with soap and water, and protects metals coated with it 
from the action of the atmosphere. Zapon may also be colored, 
but, of course, only with coloring substances — mostly aniline 
colors — which are soluble in the solvent used for the cellulose. 

A similar preparation is known as kristaline. It is a hard, 
transparent enamel, which can be applied as a lacquer in all 



488 ELECTRO-DEPOSITION OF METALS. 

kinds of metal- work without affecting the most delicate finish. It 
is applied by dipping, is invisible, and leaves no mark in drying. 

Kristaline has now been in use for some ten years, and can 
be relied upon to protect all metal-work from acids and 
alkalies, also coal-gas, alcohol, benzine, oil, water, fly-specks, 
etc. It is especially designed to prevent the highest class of 
metal-work from tarnishing and to preserve the delicate 
shades of color produced by electricity and artificial oxidation. 

A lacquer similar to zapon or kristaline may be prepared by 
substituting soluble pyroxylin for cellulose, the process being 
as follows : Bring collodion-cotton, i. e., soluble pyroxylin, such 
as is used by photographers, into a box which can be hermetic- 
ally closed, and place upon the bottom of the box a dish with 
sulphuric acid. The purpose of this is to dry the collodion- 
cotton, which requires from 36 to 48 hours. The collodion- 
cotton is then brought into a large bottle, and three to four 
times its quantity by weight of very strong alcohol poured over 
it. In a few days the greater portion of it is dissolved, when 
the clear solution is poured into another bottle. Add to the 
clear solution more collodion-cotton, about 25 to 30 per cent, 
of the weight of the quantity originally used, and the resulting 
product forms an excellent cellulose lacquer, which rapidly 
hardens to a perfectly transparent and very glossy coating. 
For diluting cellulose lacquers it is best to use wood spirit. To 
color them, dissolve an aniline color in strong spirits of wine, 
add a corresponding quantity of the solution to the lacquer, 
and shake vigorously. 

For lacquering articles by dipping, they should be as clean 
as for plating, and so arranged that the lacquer will run off 
properly. Allow them to drip over the drip tank until the 
lacquer stops flowing. Dry in a temperature of ioo° F., if 
possible, using a thermometer. Dip lacquers will dry in the 
air, but baking improves the finish. Use a tin-lined wooden 
tank for holding the lacquer, or a chemically enameled iron 
tank or a glass tank. When not in use cover with a wooden or 
sheet galvanized cover. 






CHAPTER XVI. 

HYGIENIC RULES FOR THE WORKSHOP. 

In but few other branches of industry has the workman 
so constantly to deal with powerful poisons, as well as other 
substances and vapors, which are exceedingly corrosive in 
their action upon the skin and the mucous membranes, as in 
electro-plating. However, with ordinary care and sobriety, 
all influences injurious to health may be readily overcome. 

The necessity of frequently renewing the air in the workshop 
by thorough ventilation has already been referred to in Chapter 
IV., " Electro-plating establishments in general." Workmen 
exclusively engaged in pickling objects are advised to neutral- 
ize the action of the acid upon the enamel of the teeth and the 
mucous membranes of the mouth and throat by frequently rins- 
ing the mouth with dilute solution of bicarbonate of soda. 
Workmen engaged in freeing the objects from grease lose, for 
want of cleanliness, the skin on the portions of the fingers 
which come constantly in contact with the lime and caustic 
lyes. This may be overcome by frequently washing the hands 
in clean water, and previous to each intermission in the work, 
the workman should, after washing the hands, dip them in dilute 
sulphuric acid, dry them, and thoroughly rub them with cos- 
moline, or a mixture of equal parts of glycerine and water. 
The use of rubber gloves by workmen engaged in freeing the 
objects from grease cannot be recommended, they being ex- 
pensive and subject to rapid destruction. It is better to wrap 
a linen rag seven or eight times around a sore finger, many 
workmen using this precaution to protect the skin from the 
corrosive action of the lime. 

It should be a rule for every workman employed in an 

( 489 ) 



49° ELECTRO-DEPOSITION OF METALS. 

electro-plating establishment not to drink from vessels used in 
electroplating manipulations ; for instance, porcelain dishes, 
beer glasses, etc. One workman may this moment use such a 
vessel to drink from, and without his knowledge another may 
employ it the next moment for dipping out potassium cyanide 
solution, and the first using it again as a drinking vessel may 
incur sickness or even fatal poisoning. The handling of potas- 
sium cyanide and its solutions requires constant care and judg- 
ment. Working with sore hands in such solutions should be 
avoided as much as possible ; but if it has to be done, and the 
workman feels a sharp pain in the sore, wash the latter quickly 
with clean water and apply a few drops of green vitriol solu- 
tion. Many individuals are very sensitive to nickel solutions, 
eruptions which are painful and heal slowly breaking out 
upon the arms and hands, while others may for years come in 
contact with nickel baths without being subject to eruptions. 
In such case prophylaxis is also the safeguard, i. e., to prevent 
by immediate thorough washing the formation of the eruption 
if the skin has been brought in contact with the nickel solution, 
as, for instance, in taking out with the hand an object which 
has dropped into a nickel bath. 

Below will be found some directions for neutralizing, in case 
of internal poisoning, the effects of the poison either entirely or 
at least sufficiently to retard its action until professional aid can 
be summoned. 

Poisoning by hydrocyanic {prussic) acid, potassium cyanide, 
or cyanides. — If prussic acid, or the cyanides, be concentrated 
or have been absorbed in considerable quantity, their action is 
almost instantly fatal, and there is little hope of saving the 
victim, although everything possible should be tried. But if 
these substances have been taken in very dilute condition, 
they may not prove immediately fatal, and there is some hope 
that remedial measures may be successfully applied. 

In poisoning with these substances, water as cold as possible 
should be run upon the head and spine of the patient, and he 
should be made to inhale, carefully and moderately, the vapor 



HYGIENIC RULES FOR THE WORKSHOP. 49 1 

of chlorine water, bleaching powder, or Javelle water (hypo- 
chlorite of soda). 

Should these poisons be introduced into the stomach, there 
should be administered as soon as possible the hydrate of 
sesquioxide of iron, or, what is better, dilute solutions of the 
acetate, citrate, or tartrate of iron. With proper precautions a 
very dilute solution of sulphate of zinc may be given. 

Poisoning by copper-salts. — The stomach should be quickly 
emptied by means of an emetic or, in want of this, the patient 
should thrust his finger to the back of his throat and induce 
vomiting by tickling the uvula. After vomiting drink milk, 
white of egg, gum-water, or some mucilaginous decoction. 

Poisoning by lead-salts requires the same treatment as poison- 
ing by copper-salts. Lemonade of sulphuric acid or an alkaline 
solution containing carbonic acid, such as Vichy water or bicar- 
bonate of soda, is also very serviceable. 

Poisoning by arsenic. — The stomach must be quickly emptied 
by an energetic emetic, when freshly precipitated ferric hydrate 
and calcined magnesia may be given as an antidote. Calcined 
magnesia being generally on hand, mix it with 15 or 20 times 
the quantity of water, and give this mixture 3 to 6 tablespoon- 
iuls every 10 to 15 minutes. 

Poisoning by alkalies. — Use weak acids, such as vinegar, 
lemon-juice, etc., and in their absence sulphuric, hydrochloric 
or nitric acid diluted to the strength of lemonade. After the 
pain in the stomach has diminished, it will be well to admin- 
ister a few spoonfuls of olive oil. 

Poisoning by mercury salts. — Mercury salts, and particularly 
the chloride (corrosive sublimate), form with the white of egg 
(albumen) a compound very insoluble and inert. The remedy, 
albumen, is therefore indicated. Sulphur and sulphuretted 
water are also serviceable for the purpose. 

Poisoning by sulphuretted hydrogen. — The patient should be 
made to inhale the vapor of chlorine from chlorine water, 
Javelle water, or bleaching-powder. Energetic friction, espe- 
cially at the extremities of the limbs, should be employed. 



492 ELECTRO-DEPOSITION OF METALS. 

Large quantities of warm and emollient drinks should be given, 
and abundance of fresh air. 

Poisoning by chlorine, sulphurotis acid, nitrous and hyponitric 
gases. — Admit immediately an abundance of fresh air, and ad- 
minister light inspirations of ammonia. Give plenty of hot 
drinks and excite friction, in order to conserve the warmth and 
transpiration of the skin. Employ hot foot-baths to remove 
the blood from the lungs. Afterwards maintain in the mouth 
of the patient some substance which, melting slowly, will keep 
the throat moist, such as jujube and marshmallow paste, 
molasses candy, and licorice paste. Milk is excellent. 



CHAPTER XVII. 

CHEMICAL PRODUCTS AND VARIOUS APPARATUS AND INSTRU- 
MENTS USED IN ELECTRO-PLATING. 

A. Chemical Products. 

Below the characteristic properties of the chemical products 
employed in the workshop will be briefly discussed, and the 
reactions indicated which allow of their recognition. It fre- 
quently happens that the labels become detached from the 
bottles and boxes, thus rendering the determination of their 
contents necessary. 

I. Acids. 

I. Sulphuric acid (oil of vitriol). — Two varieties of this acid 
are found in commerce, viz., fuming sulphuric acid (disulphuric 
acid), and ordinary sulphuric acid. The first is a thick oily 
fluid generally colored yellowish by organic substances, and 
emits dense white vapors in the air. Its specific gravity is 
1.87 to 1.89. The only purpose for which fuming sulphuric 
acid is used in the electro-plating art is as a mixture with 
nitric acid, for stripping silvered objects. 

Ordinary sulphuric acid has a specific gravity of 1.84. 
Diluted with water it serves for filling the Bunsen elements and 
as a pickle for iron ; in a concentrated state it is used in the 
preparation of pickles and as an addition to the galvanoplastic 
copper bath. The crude commercial acid generally contains 
arsenic, hence care must be had to procure a pure article. In 
diluting the acid with water, it should in all cases be added to 
the water in a very gentle stream and with constant stirring, as 
otherwise a sudden generation of steam of explosive violence 
might result, and the dangerous corrosive liquid be scattered in 
all directions. Concentrated sulphuric acid vigorously attacks 

(493 ) 



494 ELECTRO-DEPOSITION OF METALS. 

all organic substances, and hence has to be kept in bottles with 
glass stoppers, and bringing it in contact with the skin should 
be carefully avoided. 

Recognition. — One part of the acid mixed with 25 parts of 
distilled water gives, when compounded with a few drops of 
barium chloride solution, a white precipitate of barium sul- 
phate. 

2. Nitric acid (aqua fortis, spirit of nitre). — It is found in 
trade of various degrees of strength. For our purposes acid 
of 40 and 30 Be., is generally used. The acid is usually a 
more or less deep yellow, and frequently contains chlorine. 
The vapors emitted by nitric acid are poisonous and of a 
characteristic odor, by which the concentrated acid is readily 
distinguished from other acids. It is used for filling the Bun- 
sen elements (carbon in nitric acid), and for pickling in com- 
bination with sulphuric acid and chlorine. On coming in con- 
tact with the skin it produces yellow stains. 

Recognition. — By heating the not too dilute acid with copper, 
brown-red vapors are evolved. For the determination of dilute 
nitric acid, add a few drops of it to green vitriol solution, when 
a black-brown coloration will be produced on the point of con- 
tact. 

3. Hydrochloric acid {muriatic acid). — The pure acid is a 
colorless fluid which emits abundant fumes in contact with the 
air, and has a pungent odor by which it is readily distinguished 
from other acids. The specific gravity of the strongest hydro- 
chloric acid is 1.2. The crude acid of commerce has a yellow 
color, due to iron, and contains arsenic. Dilute hydrochloric 
acid is used for pickling iron and zinc. 

Recognition. — On adding to the acid very much diluted with 
distilled water a few drops of solution of nitrate of silver in dis- 
tilled water, a heavy white precipitate is formed, which becomes 
black by exposure to the light. 

4. Hydrocyanic acid ( pn/ssic acid). — This extremely pois- 
onous acid exists in nature only in a state of combination in 
certain vegetables and fruits, and especially in the kernels of 



CHEMICAL PRODUCTS AND APPARATUS USED. . 495 

the latter, as, for instance, in the peach, the berries of the 
cherry laurel, bitter almonds, the stones of the apricot, of 
plums, cherries, etc. It may be obtained anhydrous, but, in 
this state it is useless, and very difficult to preserve from de- 
composition. Diluted hydrocyanic acid is coloress, with a 
bitter taste and the characteristic smell of bitter almonds. It 
is employed in the preparation of gold immersing baths, and 
for the decomposition of the potassa in old silver baths. The 
inhalation of the vapors of this acid may have a fatal effect, as 
also its coming in contact with wounds. 

Recognition. — By its characteristic smell of bitter almonds. 
Or mix it with potash lye until blue litmus paper is no longer 
reddened, then add solution of green vitriol which has been 
partially oxidized by standing in the air, and acidulate with 
hydrochloric acid. A precipitate of Berlin blue is formed. 

5. Citric acid. — Clear colorless crystals of 1.542 specific 
gravity, which dissolve with great ease in both hot and cold 
water. It is frequently employed for acidulating nickel baths, 
and, combined with sodium citrate, in the preparation of plat- 
inum baths. 

Recognition. — Lime-water compounded with aqueous solution 
of citric acid remains clear in the cold, but on boiling deposits 
a precipitate of calcium citrate. The precipitate is soluble in 
ammonium chloride, but on boiling is again precipitated, and 
is then insoluble in sal ammoniac. 

6. Boric acid (boracic acid). — This acid is found in com- 
merce in the shape of scales with nacreous lustre and greasy 
to the touch ; when obtained from solutions by evaporation, it 
forms colorless prisms. Its specific gravity is 1.435; ft dis- 
solves with difficulty in cold water (1 part of acid requiring, at 
64. 4 F., 28 of water), but is more rapidly soluble in boiling 
water (^i part of acid requiring 3 of water at 21 2° F.). Ac- 
cording to Weston's proposition, boric acid is employed as an 
addition to nickel baths, etc. 

Recognition. — By mixing solution of boric acid in water with 
some hydrochloric acid and dipping turmeric paper in the solu- 



496 ELECTRO-DEPOSITION OF METALS. 

tion, the latter acquires a brown color, the color becoming 
more intense on drying. Alkalies impart to turmeric paper a 
similar coloration, which, however, disappears on immersing 
the paper in dilute hydrochloric acid. 

7. Arsenious acid {white arsenic, arsenic, ratsbane). — It gen- 
erally occurs in the shape of a white powder, and sometimes in 
vitreous-like lumps, resembling porcelain. For our purposes 
the white powder is almost exclusively used. It is slightly sol- 
uble in cold water, and more readily so in hot water and hy- 
drochloric acid. Notwithstanding its greater specific gravity, 
(3.7) only a portion of the powder sinks to the bottom on 
mixing it with water, another portion being retained on the 
surface by air bubbles adhering to it. It is employed as an 
addition to brass baths, further, in the preparation of arsenic 
baths, for blacking copper alloys, and in certain silver whiten- 
ing baths. 

Recognition. — When a small quantity of arsenious acid is 
thrown upon glowing coals an odor resembling that of garlic is 
perceptible. By mixing solution of arsenious acid, prepared by 
boiling with water, with a few drops of ammoniacal solution of 
nitrate of silver, a yellow precipitate of arsenate of silver is ob- 
tained. The ammoniacal solution of nitrate of silver is pre- 
pared by adding ammonia to solution of nitrate of silver until 
the precipitate at first formed disappears. 

8. Chromic acid.- — It forms crimson-red needles, and also 
occurs in commerce in the shape of a red powder. It is read- 
ily soluble in water, forming a red fluid which serves for filling 
batteries. 

Recognition. — Chromic acid can scarcely be mistaken for any 
other chemical product employed by the electro-plater. A 
very much diluted solution of it gives, after neutralization with 
caustic alkali and adding a few drops of nitrate of silver solution, 
a crimson-red precipitate of chromate of silver. 

9. Hydrofluoric acid. — A colorless, corrosive, very mobile 
liquid of a sharp, pungent odor. The anhydrous acid fumes 
strongly in the air and attracts moisture with avidity. Hydro- 



CHEMICAL PRODUCTS AND APPARATUS USED. . 497 

fluoric acid is used for etching glass and for pickling aluminium 
dead white. Great care must be observed in working with the 
acid, since not only the aqueous solution, but also the vapors, 
have an extremely corrodent effect upon the skin and respira- 
tory organs. 

Recognition. — By covering a small platinum dish containing 
hydrofluoric acid with a glass-plate free from grease, the latter 
in half an hour appears etched. 

II. Alkalies and Alkaline Earths. 

10. Potassium hydrate (caustic potash). — It is found in com- 
merce in various degrees of purity, either in sticks or cakes. 
It is very deliquescent, and dissolves readily in water and alco- 
hol ; by absorbing carbonic acid from the air it rapidly becomes 
converted into the carbonate, and thus loses its caustic proper- 
ties. It should, therefore, be kept in well-closed vessels. 
Substances moistened with solution of caustic potash give rise 
to a peculiar soapy sensation of the skin when touched. It 
should never be allowed to enter the mouth, as even dilute 
solutions almost instantaneously remove the lining of tender 
skin. Should such an accident happen, the mouth should be 
at once several times rinsed with water and then with very di- 
lute acetic acid. Pure caustic potash serves as an addition to 
zinc baths, gold baths, etc. For the purpose of freeing objects 
irom grease the more impure commercial article is used. 

11. Sodium hydrate (caustic soda). — It also occurs in com- 
merce in various degrees of purity, either in sticks or lumps. 
It is of a highly caustic character, resembling potassium hydrate 
(see above) in properties and effects. It is employed for free- 
ing objects from grease. 

12. Ammonium hydrate {ammonia or spirits of hartshorn). 
— It is simply water saturated with ammonia gas. By expos- 
ure ammonia gas is gradually evolved, so that it must be kept 
in closely-stoppered bottles, in order to preserve the strength 
of the solution unimpaired. Four qualities are generally found 
in commerce, viz., ammonia of 0.910 specific gravity (contain- 

32 



49 8 ELECTRO-DEPOSITION OF METALS. 

ing 24.2 per cent, of ammonia gas) ; of 0.920 specific gravity 
(with 21.2 per cent, of ammonia gas) ; of 0.940 specific gravity 
(with 15.2 per cent, of ammonia gas); and 0.960 specific 
gravity (with 9.75 per cent, of ammonia gas). It is employed 
for neutralizing nickel and cobalt baths when too acid, in the 
preparation of fulminating gold, and as an addition to some 
copper and brass baths. 
Recognition. — By the odor. 

13. Calcium hydrate {burnt or quick lime). — It forms hard, 
white to gray pieces, which on moistening with water crumble 
to a light white powder, evolving thereby much heat. Vienna 
lime is burnt lime containing magnesia. Lime serves for free- 
ing objects from grease, and for this purpose is made into a 
thinly-fluid paste with chalk and water with which the objects 
to be freed from grease are brushed. Vienna lime is much 
used as a polishing agent. 

III. Sulphur Combinations. 

14. Sulphuretted hydrogen (sulphydric acid, hydrosulphuric 
acid). — A very poisonous colorless gas with a fetid smell re- 
sembling that of rotten eggs. Ignited in the air, it burns with 
a blue flame, sulphurous acid and water being formed. At the 
ordinary temperature water absorbs about three times its own 
volume of the gas, and then acquires the same properties as the 
gas itself. Sulphuretted hydrogen serves for the metallizing of 
moulds as described on p. 455, where the manner of evolving 
it is also given. It is sometimes employed for the production 
of " oxidized " silver. Care should be taken not to bring 
metallic salts, gilt or silvered articles, or pure gold and silver 
in contact with sulphuretted hydrogen, they being rapidly sul- 
phurized by it. 

Recognition. — By its penetrating smell ; further, by a strip of 
paper moistened with sugar of lead solution becoming black 
when brought into a solution of sulphuretted hydrogen or an 
atmosphere containing it. 

15. Potassium sulphide (liver of sulphur}. — It forms a hard 



CHEMICAL PRODUCTS AND APPARATUS USED. 499 

green-yellow to pale brown mass, with conchoidal fracture. It 
readily absorbs moisture, whereby it deliquesces and smells of 
sulphuretted hydrogen. It is employed for coloring copper 
and silver black. 

Recognition. — On pouring an acid over liver of sulphur, sul- 
phuretted hydrogen is evolved with effervescence, sulphur being 
at the same time separated. 

16. Ammonium sulphide {sulphydrate or hydro sulphate of 
ammonia). — When freshly prepared it forms a clear and color- 
less fluid, with an odor of ammonia and sulphuretted hydrogen ; 
by standing it becomes yellow, and, later on, precipitates sul- 
phur. It is used for the same purpose as liver of sulphur. 

17. Carbon disulphide or bisulphide. — Pure carbon disulphide 
is a colorless and transparent liquid, which is very dense, and 
exhibits the property of double refraction. Its smell is charac- 
teristic and most disgusting, and may be compared to that of 
rotten turnips. It burns with a blue flame of sulphurous acid, 
carbonic acid being at the same time produced. It is used as 
a solvent for phosphorus and caoutchouc in metallizing moulds 
according to Parkes' method. This solution should be very 
carefully handled. 

18. Antimony sulphide. — a. Black sulphide of antimony 
{stibium sulfuratum nigrum) is found in commerce in heavy, 
gray and lustreless pieces or as a fine black-gray powder, with 
slight lustre. It serves for the preparation of antimony baths, 
and for coloring copper alloys black. 

b. Red sulphide of antimony {stibium sulfuratum auran- 
tiacum) forms a delicate orange-red powder without taste or 
odor; it is insoluble in water, but soluble in ammonium sul- 
phide, spirits of hartshorn and alkaline lyes. In connection 
with ammonium sulphide or ammonia it serves for coloring 
brass brown. 

19. Arsenic trisulphide or arsenious sulphide {orpiment). — It 
is found in commerce in the natural, as well as artificial, state, 
the former occurring mostly in kidney-shaped masses of a 
lemon color, and the later in more orange-red masses, or as a 



500 ELECTRO-DEPOSITION OF METALS. 

dull yellow powder. Specific gravity 3.46. It is soluble in the 
alkalies and spirits of sal ammoniac. 

20. Ferric sulphide. — Hard black masses generally in flat 
plates, which are only used for the evolution of sulphuretted 
hydrogen. 

IV. Chlorine Combinations. 

21. Sodium chloride {common salt, rock salt.) — The pure salt 
should form white cubical crystals, of which 100 parts of cojd 
water dissolve 36, hot water dissolving slightly more. The 
specific gravity of sodium chloride is 2.2. In electroplating 
sodium chloride is employed as a conducting salt for some gold 
baths, as a constituent of argentiferous pastes, and for precipi- 
tating the silver as chloride from argentiferous solutions. 

Recognition. — An aqueous solution of sodium chloride on 
being mixed with a few drops of lunar caustic solution yields a 
white caseous precipitate, which becomes black by exposure to 
light, and does not disappear by the addition of nitric acid, but 
is dissolved by ammonia in excess. 

22. Ammonium chloride {sal ammoniac) . — A white substance 
found in commerce in the shape of tough fibrous crystals. It 
has a sharp saline taste, and is soluble in 2^ parts of cold, and 
in a much smaller quantity of hot water. By heat it is sub- 
limed without decomposition. It serves for soldering and tin- 
ning, and as a conducting salt for many baths. 

Recognition. — By sublimation on heating. By adding to a 
saturated solution of the salt a few drops of solution of platinum 
chloride, a yellow precipitate of platoso-ammonium chloride is 
formed. 

23. Antimony trichloride {butter of antimony). — A crystalline 
mass which readily deliquesces in the air. Its solution in hydro- 
chloric acid yields the liquor stibii chlorati, also called liquid 
butter of antimony. It has a yellowish color, and on mixing 
with water yields an abundant white precipitate, soluble in pot- 
ash lye. The solution serves for coloring brass steel-gray, and 
for browning gun-barrels. 






CHEMICAL PRODUCTS AND APPARATUS USED. 501 

24. Arsenions chloride. — A thick oily fluid, which evaporates 
in the air with the emission of white vapors. 

25. Copper chloride. — Blue-green ctystals readily soluble in 
water. The concentrated solution is green, and the dilute solu- 
tion blue. On evaporating to dryness, brown-yellow copper 
chloride is formed. It is employed in copper and brass baths 
as well as for patinizing, 

26. Tin chloride. — a. Stannous chloride or tin salt. A white 
crystalline salt readily soluble in water, but its solution on ex- 
posure to the air becomes turbid ; by adding, however, hydro- 
chloric acid, it again becomes clear. On fusing the crystallized 
salt loses its water of crystallization, and forms a solid non- 
transparent mass of a pale yellow color — the fused tin salt. 
The crystallized, as well as the fused, salt serves for the prepa- 
ration of brass, bronze and tin baths. 

Recognition. — By pouring hydrochloric acid over a small 
quantity of tin salt and adding potassium chromate solution, 
the solution acquires a green color. By mixing dilute tin salt 
solution with some chlorine water and adding a few drops of 
gold chloride solution, purple of Cassius is precipitated ; very 
dilute solutions acquire a purple color. 

b. Stannic chloride occurs in commerce in colorless crystals, 
and in the anhydrous state forms a yellowish, strongly fuming 
caustic liquid known as the " fuming liquor of Libadius." 

27. Zinc chloride ( hydrochlor ate or muriate of zi7ic ; butter of 
zinc). — A white crystalline or fused mass which is very soluble 
and deliquescent. The salt prepared by evaporation generally 
contains some zinc oxychloride, and hence does not yield an 
entirely clear solution. It serves for preparing brass and zinc 
baths, and its solution for nickeling by immersion, soldering, 
etc. 

Recognition. — Solution of caustic potash separates a volum- 
inous precipitate of zinc oxhydrate, which redissolves in an 
excess of the caustic potash solution. By conducting sul- 
phuretted hydrogen into a solution of a zinc salt acidulated 
with acetic acid, a precipitate of white zinc sulphide is formed. 



502 ELECTRO-DEPOSITION OF METALS. 

28. Zinc chloride and ammonium chloride. — This salt is a 
combination of zinc chloride with sal ammoniac, and forms a 
white very deliquescent powder. Its solution serves for solder- 
ing and for zincking by contact. 

29. Nickel chloride. — It is found in commerce in the shape 
of deep green crystals and of a pale green powder. The latter 
contains considerably less water and less free acid than the 
crystallized article, and is to be preferred for electro-plating 
purposes. The crystallized salt dissolves readily in water, and 
the powder somewhat more slowly. Should the solution of the 
latter deposit a yellow precipitate, consisting of basic nickel 
chloride, it has to be brought into solution by the addition of 
a small quantity of hydrochloric acid. Nickel chloride is em- 
ployed for nickel baths. 

Recognition. — By mixing the green solution of the salt with 
some spirits of sal ammoniac, a precipitate is formed, which 
dissolves in an excess of spirits of sal ammoniac, the solution 
showing a deep blue color. 

30. Cobalt chloride. — It forms small rose-colored crystals, 
which, on heating, yield their water of crystallization, and are 
converted into a blue mass. The crystals are readily soluble 
in water, while the anhydrous blue powder dissolves slowly. 
Cobalt chloride is employed for the preparation of cobalt 
baths. 

Recognition. — Caustic potash precipitates from a solution of 
cobalt chloride a blue basic salt which is gradually converted 
into a rose-colored hydrate, and, with the access of air, into 
green- brown cobaltous hydrate. The aqueous solution yields 
with solution of yellow prussiate of potash a pale gray-green 
precipitate. 

31. Silver chloride. — A heavy white powder which by ex- 
posure to light becomes gradually blue-gray, then violet and 
finally black. When precipitated from silver solutions, a case- 
ous precipitate is separated. At 500 F. it fuses without being 
decomposed, to a yellowish fluid which, on cooling, congeals 
to a transparent, tenacious, horn-like mass. Silver chloride is 



CHEMICAL PRODUCTS AND APPARATUS USED. , 503 

practically insoluble in water, but dissolves with ease in spirits 
of sal ammoniac and in potassium cyanide solution. It is em- 
ployed in the preparation of baths for silver-plating, for silver- 
ing by boiling, and in the pastes for silvering by friction. 

Recognition. — By its solubility in ammonia, pulverulent 
metallic silver being separated from the solution by dipping in 
it bright ribands of copper. 

32. Gold chloride (ter chloride of gold, muriate of gold, auric 
chloride). — This salt occurs in commerce as crystallized gold 
chloride of an orange-yellow color, and as a brown crystalline 
mass, which is designated as neutral gold chloride, or as gold 
chloride free from acid, while the crystallized article always 
contains acid, and, hence, should not be used for gold baths. 
Gold chloride absorbs atmospheric moisture and becomes re- 
solved into a liquid of a fine gold color. On being moder- 
ately heated, yellowish-white aurous chloride is formed, and 
on being subjected to stronger heat it is decomposed to 
metallic gold and chlorine gas. By mixing its aqueous solu- 
tion with ammonia, a yellow-brown powder consisting of ful- 
minating gold is formed. In a dry state this powder is highly 
explosive, and, hence, when precipitating it from gold chloride 
solution for the preparation of gold baths, it must be used 
while still moist. 

Recognition. — By the formation of the precipitate of fulmi- 
nating gold on mixing the gold chloride solution with am- 
monia. Further by the precipitation of brown metallic gold 
powder on mixing the gold chloride solution with green vitriol 
solution. 

33. Platinic chloride. — The substance usually known by this 
name is hydroplatinic chloride. It forms red-brown very sol- 
uble — and in fact deliquescent — crystals, With ammonium 
chloride it forms platoso-ammonium chloride (see p. 376). 
Both combinations are used in the preparation of platinum 
baths. The solution of platinic chloride also serves for coloring 
silver, tin, brass and other metals. 

Recognition. — By the formation of a precipitate of yellow 



504 ELECTRO-DEPOSrTION OF METALS. 

platoso-ammonium chloride by mixing concentrated platinic 
chloride solution with a few drops of saturated sal ammoniac 
solution. 

V. Cyanides. 

34. Potassium cyanide (white prussiate of potash). — For 
electro-plating purposes pure potassium cyanide with 98 to 99 
per cent., as well as that containing 80, 70 and 60 per cent, is 
used, whilst for pickling the preparation with 45 per cent, is 
employed. For the preparation of alkaline copper an,d brass 
baths, as well as silver baths, the pure 98 to 99 per cent, pro- 
duct is generally employed. However, for preparing gold 
baths the 60 per cent, article is mostly preferred, because the 
potash present in all potassium cyanide varieties with a lower 
content renders fresh baths more conductive. However, gold 
baths may also be prepared with 98 per cent, potassium 
cyanide without fear of injury to the efficiency of the baths, 
while, under ordinary circumstances, a preparation with less 
than 98 per cent, may safely be used for the rest of the baths. 
However, when potassium cyanide has to be added to the 
baths, as is from time to time necessary, only the pure prepara- 
tion free from potash should be used, because the potash con- 
tained in the inferior qualities gradually thickens the bath too 
much. 

No product is more important to the electro-plater than 
potassium cyanide. The pure 98 to 99 per cent, product is a 
white transparent crystalline mass, the crystalline structure 
being plainly perceptible upon the fracture. In a dry state it 
is odorless, but when it has absorbed some moisture it has a 
strong smell of prussic acid. It is readily soluble in water, and 
should be dissolved in cold water only, since when poured into 
hot water it is partially decomposed, which is recognized by the 
appearance of an odor of ammonia. Potassium cyanide solution 
in cold water may, however, be boiled for a short time without 
suffering essential decomposition. Potassium cyanide must be 
kept in well-closed vessels, since when exposed to the air it 



CHEMICAL PRODUCTS AND APPARATUS USED. 505 

becomes deliquescent, and is decomposed by the carbonic 
acid of the air, whereby potassium carbonate is formed while 
prussic acid escapes. It is a deadly poison and must be used 
with the utmost caution. Potassium cyanide with 80, 70, 60 or 
45 per cent, forms a gray-white to white mass with a porcelain- 
like fracture. A pale gray coloration is not a proof of impur- 
ities, it being due to somewhat too high a temperature in fusing. 
These varieties are found in commerce in irregular lumps or in 
sticks, the use of the latter offering no advantage. Their be- 
havior towards the air and in dissolving is the same as that of 
the pure product. 

Recognition. — By the bitter-almond smell of the solution. By 
mixing potassium cyanide solution with ferric chloride and then 
with hydrochloric acid until the latter strongly predominates, a 
precipitate of Berlin blue is formed. 

The pure salt free from potash does not effervesce on adding 
dilute acid, which is, however, the case with the inferior 
qualities. 

To facilitate the use of potassium cyanide with a different 
content than that given in a formula for preparing a bath, the 
following table is here given : 

Potassium cyanide with 



98 per cent. 80 per cent. 70 per cent. 60 per cent. 



45 per cent. 



By we 


ght. 




By weight. 




By weight. 




By weight. 




By weight. 


1 


part 


— 


1.230 parts 


= 


1.400 parts 


= 


1.660 


parts 


= 


2.180 


parts. 


0.820 


tt 


= 


1 


= 


I.143 " 


= 


1.333 


" 


= 


1.780 


<< 


0.714 


" 


= 


0.875 P art 


= 


1. part 


= 


1. 170 


«« 


= 


I-55Q 


« 


0.615 


u 


= 


0.750 " 


= 


0.857 " 


= 


1. 


part 


= 


1.450 


« 


0.460 


u 


— 


0.562 " 


— 


0.643 " 


— 


0.750 




— 


1 


part. 



35. Copper cyanides. — There is a cuprous and a cupric cya- 
nide; that used for electro-plating purposes being a mixture of 
both. It is a green-brown powder, which should not be dried, 



506 ELECTRO-DEPOSITION OF METALS. 

since in the moist state it dissolves more readily in potassium 
cyanide. It is only used as a double salt, i. e., in combination 
with potassium cyanide in the preparation of copper, brass, 
tombac, and red gold baths. 

Recognition. — By evaporating a piece of copper cyanide the 
size of a pea, or its solution in hydrochloric acid, to dryness in 
a water bath, wherein care must be taken not to inhale the 
vapors, and dissolving the residue in water, a green-blue solu- 
tion is obtained which acquires a deep blue color by the addi- 
tion of ammonia in excess. 

36. Zinc cyanide {hydrocyanate of zinc, prussiate of zinc). — 
A white powder insoluble in water, but soluble in potassium 
cyanide, ammonia and the alkaline sulphites. The fresher it is, 
the more readily it dissolves, the dried product dissolving with 
difficulty. Its solution in potassium cyanide is used for brass 
baths. 

Recognition. — By evaporating zinc cyanide, or its solution, 
with an excess of hydrochloric acid in the water bath, zinc 
chloride remains behind, which is recognized by the same re- 
action given under zinc chloride. 

37. Silver cyanide ( prussiate, or hydrocyanate of silver). — 
A white powder which slowly becomes black when exposed to 
light. It is insoluble in water and cold acids, which, however, 
will dissolve it with the aid of heat. At 750 F., it melts to a 
dark red fluid, which, on cooling, forms a yellow mass with a 
granular structure. It is readily dissolved by potassium 
cyanide, but is only slightly soluble in ammonia, differing in 
this respect from silver chloride. It forms a double salt with 
potassium cyanide, and as such is employed in the preparation 
of silver baths. 

38. Potassium f err 0- cyanide (yellow prussiate of potash). — 
It occurs in the shape of yellow semi-translucent crystals with 
mother-of-pearl lustre, which break without noise. Exposed 
to heat they effloresce, losing their water of crystallization, and 
crumbling to a yellowish-white powder. For the solution of I 
part of the salt, 4 of water of medium temperature are required, 






CHEMICAL PRODUCTS AND APPARATUS USED. - $OJ 

the solution exhibiting a pale yellow color. It precipitates 
nearly all the metallic salts from their solutions, some of the 
precipitates being soluble in an excess of the precipitating 
agent. This salt is not poisonous. It serves for the prepara- 
tion of silver and gold baths ; its employment, however, offer- 
ing no advantages over potassium cyanide except its non- 
poisonous properties be considered as such. 

Recognition. — When the yellow solution is mixed with ferric 
chloride a precipitate of Berlin blue is formed. 

VI. Carbonates. 

39. Potassium carbonate {potash). — It is found in commerce 
in gray-white, bluish, yellowish pieces, the colorations being 
due to admixtures of small quantities of various metallic oxides. 
When pure it is in the form of a white powder or in pieces the 
size of a pea. The salt, being very deliquescent, has to be kept 
in well-closed receptacles. It is readily soluble, and, if pure, 
the solution in distilled water must be clear. It serves as an 
addition to some baths, and in an impure state for freeing ob- 
jects from grease. 

Recognition.— r The solution effervesces on the addition of 
hydrochloric acid. The solution neutralized with hydrochloric 
acid gives with platinum chloride a heavy yellow precipitate of 
platinic potassium chloride, provided the solution be not too 
dilute. 

40. Acid potassium carbonate or monopotassic carbonate, com- 
monly called bicarbonate of potash. — Colorless transparent crys- 
tals, which at a medium temperature dissolve to a clear solution 
in 4 parts of water. It is not deliquescent ; however, on boil- 
ing its solution it loses carbonic acid, and contains then only 
potassium carbonate. It is employed for the preparation of 
certain baths for gilding by simple immersion. 

41. Sodium carbonate {washing soda). — It occurs in com- 
merce as crystallized or calcined soda of various degrees of 
purity. The crystallized product forms colorless crystals or 
masses of crystals, which, on exposure to air, rapidly effloresce 



508 ELECTRO-DEPOSITION OF METALS. 

and crumble to a white powder. By heating, the crystals also 
lose their water, a white powder, the so-called calcined soda, 
remaining behind. Soda dissolves readily in water, and serves 
as an addition to copper and brass baths, for the preparation 
of metallic carbonates, and for freeing objects from grease, the 
ordinary impure soda being used for the latter purpose. 

The directions for additions of sodium carbonate to baths 
generally refer to the crystallized salt. If calcined soda is to 
be used instead, 0.4 part of it will have to be taken for 1 part 
of the crystallized product. 

42. Sodium bicarbonate {baking powder). — A dull white 
powder soluble in 10 parts of water of 68° F. On boiling, the 
solution loses one-half of its carbonic acid, and then contains 
sodium carbonate only. 

43. Calcium carbonate {marble, chalk). — When pure it forms 
a snow-white crystalline powder, a yellowish color indicating a 
content of iron. It is insoluble in water, but soluble, with 
effervescence, in hydrochloric, nitric and acetic acids. In 
nature, calcium carbonate occurs as marble, limestone, chalk. 

In the form of whiting (ground chalk carefully freed from all 
stony matter) it is used for the removal of an excess of acid in 
acid copper baths, and mixed with burnt lime as an agent for 
freeing objects from grease. 

44. Copper carbonate. — Occurs in nature as malachite and 
allied minerals. The artificial carbonate is an azure-blue sub- 
stance, insoluble in water, but soluble, with effervescence, in 
acids. Copper carbonate precipitated from copper solution 
by alkaline carbonates has a greenish color. Copper carbon- 
ate is employed for copper and brass baths, and for the re- 
moval of an excess of acid in acid copper baths. 

Recognition. — Dissolves in acids with effervescence ; on dip- 
ping a riband of bright sheet-iron in the solution, copper 
separates upon the iron. On compounding the solution with 
ammonia in excess, a deep blue coloration is obtained. 

45. Zinc carbonate. — A white powder, insoluble in water. 
The product obtained by precipitating a zinc salt with alkaline 






CHEMICAL PRODUCTS AND APPARATUS USED. ' 509 

carbonates is a combination of zinc carbonate with zinc oxy- 
hydrate. It serves for brass baths in connection with potassium 
cyanide. 

Recognition. — In a solution in hydrochloric acid, which is 
formed with effervescence, according to the reactions given 
under zinc chloride (27). 

46. Nickel carbonate. — A pale apple- green powder, insoluble 
in water, but soluble, with effervescence, in acids. It is em- 
ployed for neutralizing nickel baths which have become acid. 

Recognition. — In hydrochloric acid, it dissolves, with effer- 
vescence, to a green fluid. By the addition of a small quantity 
of ammonia, nickel oxyhydrate is precipitated, which, by add- 
ing ammonia in excess, is redissolved, the solution showing a 
blue color. 

47. Cobalt carbonate. — A reddish powder, insoluble in water, 
but soluble in acids, the solution forming a red fluid. 

VII. Sulphates and Sulphites. 

48. Sodium sulphate {Glauber's salt). — Clear crystals of a 
slightly bitter taste, which effloresce by exposure to the air. 
They are readily soluble in water. On heating, the crystals 
melt in their water of crystallization, and when subjected to a 
red heat, calcined Glauber's salt remains behind. It is used as 
an addition to some baths. 

49. Ammonium sulphate. — It forms a neutral colorless salt, 
which is constant in the air, readily dissolves in water, and 
evaporates on heating. It serves as a conducting salt for 
nickel, cobalt and zinc baths. 

Recognition. — By its evaporating on heating. A concentrated 
solution compounded with platinic chloride gives a yellow pre- 
cipitate of platoso-ammonium chloride, while a solution mixed 
with a few drops of hydrochloric acid gives with barium chlor- 
ide a precipitate of barium sulphate. 

50. Ammonium-potassium sulphate {potash- alum). — Color- 
less crystals or pieces of crystals with an astringent taste. It is 
soluble in water, 12 parts of it dissolving in 100 parts of water 



5IO ELECTRO-DEPOSITION OF METALS. 

at the ordinary temperature. On heating, the crystals melt, 
and are converted into a white spongy mass, the so-called 
burnt alum. Potash-alum serves for the preparation of zinc 
baths and for brightening the color of gold. 

Recognition. — On adding sodium phosphate to the solution of 
this salt a jelly-like precipitate of aluminium phosphate is formed, 
which is soluble in caustic potash, but insoluble in acetic acid. 

51. Ammonium- alum is exactly analogous to the above, 
the potassium sulphate being simply replaced by ammonium 
sulphate. It is for most purposes interchangeable with potash- 
alum. On exposing ammonium-alum to a red heat, the ammo- 
nium sulphate is lost, pure alumina remaining behind. Ammo- 
nium-alum is used for preparing a bath for zincking iron and 
steel by immersion. 

Recognition. — The same as potash -alum. On heating the 
comminuted ammonium-alum with potash lye, an odor of am- 
monia becomes perceptible. 

52. Ferrous sulphate {sulphate of iron, protosulphate of iron, 
copperas, green vitriol). — Pure ferrous sulphate forms bluish- 
green transparent crystals of a sweetish astringent taste, which 
readily dissolve in water, and effloresce and oxidize in the air. 
The crude article forms green fragments frequently coated 
with a yellow powder. It generally contains, besides ferrous 
sulphate, the sulphate of copper and of zinc, as well as ferric 
sulphate. Ferrous sulphate is employed in the preparation of 
iron baths, and for the reduction of gold from its solutions. 

Recognition. — By compounding the green solution with a few 
drops of concentrated nitric acid, a black-blue ring is formed on 
the point of contact. On mixing the lukewarm solution with 
gold chloride, gold is separated as a brown powder, which by 
rubbing acquires the lustre of gold. 

53. Iron-ammonium sulphate. — Green crystals which are con- 
stant in the air and do not oxidize as readily as green vitriol. 
100 parts of water dissolve 16 parts of this salt. It is used for 
the same purposes as green vitriol. 

54. Copper sulphate {cupric sulphate, blue vitriol, or blue cop- 



CHEMICAL PRODUCTS AND APPARATUS USED. 5 I I 

peras). — It forms large blue crystals, of which 190 parts of cold 
water dissolve about 40 parts, and the same volume of hot water 
about 200 parts. Blue vitriol which does not possess a pure 
blue color, but shows a greenish lustre, is contaminated with 
green vitriol, and should not be used for electro-plating pur- 
poses. Blue vitriol serves for the preparation of alkaline cop- 
per and brass baths, acid copper baths, etc. 

Recognition. — By its appearance, as it can scarcely be mis- 
taken for anything else. A content of iron is recognized by 
boiling blue vitriol solution with a small quantity of nitric acid, 
and adding spirits of sal ammoniac in excess ; brown flakes in- 
dicate iron. 

55. Cuprous sulphite. — A brownish red crystalline powder 
formed by treating cuprous hydrate with sulphurous acid solu- 
tion. It is insoluble in water, but readily soluble in potassium 
cyanide, with only slight evolution of cyanogen. It serves for 
the preparation of alkaline copper baths in place of basic 
acetate of copper (verdigris'), blue vitriol, or cuprous oxide. 

56. Zinc sulphate (white vitriol). — It forms small colorless 
prisms of a harsh metallic taste, which readily oxidize on ex- 
posure to the air. By heating the crystals melt, and by heat- 
ing to a red heat they are decomposed into sulphurous acid and 
oxygen, which escape, while zinc oxide remains behind as resi- 
due. 100 parts of water dissolve about 50 parts of zinc sul- 
phate in the cold, and nearly 100 parts at the boiling-point. Zinc 
sulphate is employed for the preparation of brass and zinc 
baths, as well as for matt pickling. 

Recognition. — By mixing zinc sulphate solution with acetic 
acid and conducting sulphuretted hydrogen into the mixture, a 
white precipitate of zinc sulphide is formed. A slight content 
of iron is recognized by the zinc sulphate solution, made alka- 
line by ammonia, giving with ammonia sulphide a somewhat 
colored precipitate instead of a pure white one. However, a 
slight content of iron does no harm. 

57. Nickel sulphate. — Beautiful dark green crystals, readily 
soluble in water, the solution exhibiting a green color. On 



512 ELECTRO-DEPOSITION OF METALS. 

heating the crystals to above 536 F., yellow anhydrous nickel 
sulphate remains behind. Like the double salt described be- 
low, it serves for the preparation of nickel baths and for color- 
ing zinc. 

Recognition. — By compounding the solution with ammonia 
the green color passes into blue. Potassium carbonate pre- 
cipitates pale green basic nickel carbonate, which dissolves on 
adding ammonia in excess, the solution showing a blue color. 
A content of copper is recognized by the separation of black- 
brown copper sulphide on introducing sulphuretted hydrogen 
into the heated solution previously strongly acidulated with 
hydrochloric acid. 

58. Nickel- ammonium sulphate. — It forms green crystals of a 
somewhat paler color than nickel sulphate. This salt dissolves 
with more difficulty than the preceding, 100 parts of water dis- 
solving only 5.5 parts of it. It is used for the same purposes 
as the nickel sulphate, and is also recognized in the same 
manner. The following reaction serves for distinguishing it 
from nickel sulphate : By heating nickel sulphate in concen- 
trated solution with the same volume of strong potash or soda 
lye, no odor of ammonia is perceptible, while nickel-ammonium 
sulphate evolves ammoniacal gas which forms dense clouds on 
a glass rod moistened with hydrochloric acid. 

59. Cobalt sulphate. — Crimson crystals of a sharp metallic 
taste. They are constant in the air and readily dissolve in 
water, the solution showing a red color. By heating, the 
crystals lose their water of crystallization without, however, 
melting, and become thereby transparent and rose-colored. 
The salt is used for cobalt baths for the electro-deposition of 
cobalt and for cobalting by contact. 

Recognition. — In the presence of ammoniacal salts, caustic 
potash precipitates a blue basic salt, which, on heating, changes 
to a rose-colored hydrate and, by standing for some time in 
the air, to a green-brown hydrate. By mixing a concentrated 
solution of the salt strongly acidulated with hydrochloric acid 
with solution of potassium nitrate, a reddish-yellow precipitate 
is formed. 



CHEMICAL PRODUCTS AND APPARATUS USED. 513 

60. Cob alt- ammonium sulphate. This salt forms crystals of 
the same color as cobalt sulphate, which, however, dissolve 
more readily in water. 

61. Sodium sulphite and bisulphite. — a. Sodium sulphite. 
Clear, colorless, and odorless crystals, which are rapidly trans- 
formed into an amorphous powder by efflorescence. The salt 
readily dissolves in water, the solution showing a slight alkaline 
reaction due to a small content of sodium carbonate. It is em- 
ployed in the preparation of gold, brass, and copper baths, for 
silvering by immersion, etc. 

Recognition. — The solution when mixed with dilute sulphuric 
acid has an odor of burning sulphur. 

b. Sodium bisulphite. — Small crystals, or more frequently in 
the shape of a pale yellow powder with a strong odor of sul- 
phurous acid and readily soluble in water. The solution shows 
a strong acid reaction and loses sulphurous acid in the air. It 
is employed in the preparation of alkaline copper and brass 
baths. 

Both the sulphite and bisulphite must be kept in well-closed 
receptacles, as by the absorption of atmospheric oxygen they 
are converted to sulphate. 

VIII. Nitrates. 

62. Potassium nitrate (saltpetre, nitre). — It forms large, pris- 
matic crystals, generally hollow, but also occurs in commerce 
in the form of a coarse powder, soluble in 4 parts of water at a 
medium temperature. The solution has a bitter, saline taste 
and shows a neutral reaction. Potassium nitrate melts at a red 
heat, and on cooling congeals to an opaque, crystalline mass. 
It is employed in the preparation of desilvering pickle and 
for producing a matt lustre upon gold and gilding. For these 
purposes it may, however, be replaced by the cheaper sodium 
nitrate, sometimes called cubic nitre or Chile saltpetre. 

Recognition. — A small piece of coal when thrown upon melt- 
ing saltpetre burns fiercely. When a not too dilute solution of 
saltpetre is compounded with solution of potassinm bitartrate 
33 



514 ELECTRO-DEPOSITION OF METALS. 

saturated at the ordinary temperature, a crystalline precipitate 
of tartar is formed. 

63. Sodium nitrate {cubic nitre or Chile saltpetre}. — Color- 
less crystals, deliquescent and very soluble in water ; the solu- 
tion shows a neutral reaction. It is used for the same purposes 
as potassium nitrate. 

64. Mercurous nitrate. — It forms small, colorless crystals, 
which are quite transparent and slightly effloresce in the air. 
On heating they melt and are transformed, with the evolution 
of yellow-red vapors, into yellow-red mercuric oxide, which, 
on further heating, entirely evaporates. With a small quantity 
of water, mercurous nitrate yields a clear solution. By the 
further addition of water it shows a milky turbidity, which, 
however, disappears on adding nitric acid. It is employed for 
quicking the zincs of the elements, and the objects previous to 
silvering, and for brightening gilding. For the same purpose 
is also used : 

65. Mercuric nitrate {nitrate of mercury}. This salt is ob- 
tained with difficulty in a crystallized form. It is generally 
sold in the form of an oily, colorless liquid which, in contact 
with water, separates a basic salt. This precipitate disappears 
upon the addition of a few drops of nitric acid, and the liquid 
becomes clear. 

Recognition. — A bright riband of copper dipped in solution 
of mercurous or mercuric nitrate becomes coated with a white 
amalgam, which disappears upon heating. 

66. Silver nitrate {lunar caustic). — This salt is found in 
commerce in three forms : either as crystallized nitrate of silver 
in thin, rhombic, and transparent plates ; or in amorphous, 
opaque, and white plates of fused nitrate ; or in small cylinders 
of a white, or gray, or black color, according to the nature of the 
mould employed, in which form it constitutes the lunar caustic 
for surgical uses. For our purposes only the pure, crystallized 
product, free from acid, should be employed. The crystals 
dissolve readily in water. In making solutions of this and 
other silver salts, only distilled water should be used ; all other 



CHEMICAL PRODUCTS AND APPARATUS USED. 515 

waters, owing to the presence of chlorine, produce a cloudiness 
or even a distinct precipitate of silver chloride. When sub- 
jected to heat the crystals melt to a colorless, oily fluid, which, 
on cooling, congeals to a crystalline mass. Silver nitrate is 
employed in the preparation of chloride and cyanide of silver 
for silver baths. The solution in potassium cyanide may also 
be used for silver baths. The alcoholic solution is employed 
for metallizing moulds. 

Recognition. — Hydrochloric acid and common salt solution 
precipitate from silver nitrate solution silver chloride, which 
becomes black on exposure to the light, and is soluble in 
ammonia. 

IX. Phosphates and Pyrophosphates. 

67. Sodium phosphate. — Large, clear crystals, which readily 
effloresce, and whose solution in water shows an alkaline solu- 
tion. It is employed in the preparation of gold baths and for 
the production of metallic phosphates for soldering. 

Recognition. — The dilute solution compounded with silver 
nitrate yields a yellow precipitate of silver phosphate. 

68. Sodium pyrophosphate. — It forms white crystals, which 
are not subject to efflorescence, and are soluble in 6 parts of 
water at a medium temperature ; the solution shows an alkaline 
reaction. Sodium pyrophosphate also occurs in commerce in 
the form of an anhydrous white powder, though it may here be 
said that the directions for preparing baths refer to the crystal- 
lized salt. It is employed in the preparation of gold, nickel- 
bronze, and tin baths. 

Recognition.— -The dilute solution compounded with silver 
nitrate yields a white instead of a yellow precipitate. 

69. Ammonium phosphate. — A colorless crystalline powder 
quite readily soluble in water; the solution should be as neutral 
as possible. A salt smelling of ammonia, as well as one show- 
ing an acid reaction, should be rejected. In is employed in the 
preparation of platinum baths. 



5 16 ELECTRO- DEPOSITION OF METALS. 

X. Salts of Organic Acids. 

70. Potassium bitartrate {cream of tartar). — The pure salt 
forms small transparent crystals, which have an acid taste, and 
are slightly soluble in water. The commercial crude tartar or 
argot, which is a by-product in the wine industry, forms gray 
or dirty red crystalline crusts. In finely powdered state, puri- 
fied tartar is called cream of tartar. It is employed for the 
preparation of the whitening silver baths, for those of tin, and 
for the silvering paste for silvering by friction. 

7 1 . Potassium- sodium tartrate (Rochelle or Seignetle salt) . — 
Clear colorless crystals, constant in the air, of a cooling bitter 
saline taste, and soluble in 2.5 parts of water of a medium tem- 
perature. The solution shows a neutral reaction. This salt is 
employed in the preparation of copper baths free from cyanide, 
as well as of nickel and cobalt baths, which are to be decom- 
posed in the single cell apparatus. 

Recognition. — By the addition of acetic acid the solution 
yields an abundant precipitate of tartar. 

72. Antimony -potassium tartrate (tartar emetic). — A white 
crystalline substance, of which 100 parts of cold water dissolve 
5 parts, while a like volume of hot water dissolves 50 parts. 
The solution shows a slightly acid reaction. The only use of 
this salt is for the preparation of antimony baths. 

Recognition. — The solution of the salt compounded with sul- 
phuric, nitric, or oxalic acid yields a white precipitate, insoluble 
in an excess of the cold acid. Sulphuretted hydrogen imparts to 
the dilute solution a red color. Hydrochloric acid effects a 
precipitate, which is redissolved by the acid in excess. 

73. Copper acetate (verdigris). — It is found in the market in 
the form of dark green crystals showing an acid reaction, or of 
a neutral bright green powder. 

The crystallized copper acetate forms opaque dark green 
prisms, which readily effloresce, becoming thereby coated with 
a pale green powder. They dissolve with difficulty in water, 
but readily in ammonia, forming a solution of a blue color. 
They dissolve readily also in potassium cyanide and alkaline 
sulphites. 






CHEMICAL PRODUCTS AND APPARATUS USED. . 517 

The neutral copper acetate forms a blue-green crystalline 
powder, imperfectly soluble in water, but readily soluble in 
ammonia, forming a solution of a blue color. 

Copper acetate is used for preparing copper and brass baths, 
for the production of artificial patinas, for coloring, gilding, etc. 

74. Lead acetate (sugar of lead). — Colorless lustrous prisms 
or needles of a nauseous sweet taste and poisonous. The 
crystals effloresce in the air, melt at 104 F., and are readily 
soluble in water, yielding a slightly turbid solution. Lead 
acetate is employed for preparing lead baths (Nobili's rings) 
and for coloring copper and brass. 

Recognition. — By compounding lead acetate solution with 
potassium chromate solution, a heavy yellow precipitate of 
lead chromate is formed. 

75. Sodium citrate. — Colorless crystals, presenting a moist 
appearance, which are readily soluble in water ; the solution 
should show a neutral reaction. This salt is employed in the 
preparation of the platinum bath according to Bottger's for- 
mula, and as conducting salt for nickel and zinc baths. 

B. Various Apparatus and Instruments. 

Glass balloons and flasks. — These are spheres of thin blown 
glass, Fig. 153, with necks of various dimensions in length and 
diameter. They are employed for heating acids, 
dissolving metals, and a great many other uses. Fig. 153. 
They should be placed upon triangular supports of 
iron and at a certain distance from the fire, from the 
direct action of which they are to be protected by 
the intervention of a piece of wire gauze or its 
equivalent. The thinner they are the more easily 
they bear sudden changes of temperature. They 
are preferable to porcelain evaporating dishes for 
dissolving gold, because there is much less danger of losing a 
part of the product by spurting. 

Evaporating dishes or capsules. — These are usually vessels of 
porcelain, and are intended to bear a high temperature. The 




5 I 8 ELECTRO-DEPOSITION OF METALS. 

best are thin and uniformly so. Like glass flasks, they should 
be supported above the fire upon an iron stand and wire gauze. 
As far as practicable they should be gradually heated and 
cooled. When taken from the fire they should be placed 
upon rings made of plaited straw. They are made with or 
without lips, and some have a socket for a wooden handle. 
Glass evaporating dishes are not durable. 

Glass jars. — These are glass vessels, generally cylindrical, 
closed at one end, and of different capacities. 

They are employed for small gilding, silvering, and electro- 
plating baths in the cold. They are handy and serviceable for 
amateurs, because their transparency permits the progress of 
the operation to be observed at all times. 

Crucibles. — These are vessels, the shape of which is gen- 
erally an inverted truncated cone, Fig. 155, the smaller end 
being closed and the larger open. Sometimes the 
FlG - *54- opening is triangular. 

Crucibles are made of many kinds of materials ; 
metals, refractory clay, stoneware, porcelain, plum- 
bago or graphite, etc. They are generally provided 
with a cover of the same material, and are raised 
above the grate bars of the furnace by means of 
bricks or cylinders of clay. Metallic crucibles may 
be heated rapidly, but the others require to have their temper- 
ature raised gradually and carefully. They are employed for the 
preparation of many salts, for the fusion of metals, etc. Non- 
metallic crucibles are rarely used for more than one operation. 
Hydrometers. — These are glass instruments resembling ther- 
mometers in outward appearance, but having a large bulb near 
the bottom. They are used for testing the specific gravity of 
liquids, or, in other words, to test their density as compared 
with that of pure water. The liquid to be tested may be placed 
in a narrow glass jar together with the hydrometer, or may be 
contained in any other vessel. The instrument floats in the 
liquid to be tested, with its bulb below the surface and its stem 
standing above the surface. This stem is graded into degrees 




CHEMICAL PRODUCTS AND APPARATUS USED. 



519 



similar to that of a thermometer, and shows the depth of the 
bulb beneath the surface. In pure water the bulb sinks down 
to the 0° mark, or to 1.000 as marked on some scales, 1. 000 
being taken to represent the density of water at a temperature 
of 6o° F. As the density of water increases by the addition of 
salts or of liquids having a greater density than water, the bulb 
is forced upwards, and the scale then registers so many degrees 
greater density than water. 

Three differently graduated hydrometers are in use, viz., 
hydrometers graded to read direct the specific gravity of 
liquids in comparison with that of water, taking this as repre- 
sented by 1. 000; hydrometers graded by a scale adopted by 
Mr. W. Twaddell, and known as Twaddell's hydrometers ; and 
hydrometers graded by a scale adopted by M. Baume, and 
named Baume's hydrometers. The difference between the 
three gradings is shown in the following table: — 



Table 


showing the readings of different 


hydrometers. 


Specific gravity. 


Baume. 


Twaddell. 


Specific gravity. 


Baume. 


Twaddell. 


.817° 


40° 





1.250 





50° 


.827 


38 


— 


1.263 


30° 


— 


.837 


36 


— 


1.300 


— 


60 


.847 


34 


— 


1-321 


35 


— 


.856 


32 


— 


i-35° 


— 


70 


.871 


30 




1.385 
1.400 


40 


— 


.880 


28 




— 


80 


892 


26 


— 


1.450 


— 


90 


-903 


24 


— 


1-454 


45 


— 


-9*5 


22 


— 


1.500 


— 


100 


.928 


20 


— 


1.532 


5o 


— 


.942 


18 


— 


I-550 


— 


no 


^955 


16 


— 


1.600 


— 


120 


.970 


14 


— 


1.618 


55 


— 


•985 


[2 


— 


1.650 




130 


1. 000 


o° or 10 


o° 


1.700 


— 


140 


1.036 


5 


— 


1. 714 


60 


— 


1.050 


— 


10 


i.75o 


— 


150 


1.075 


10 


— 


1.800 


— 


160 


1. 100 


— 


20 


1.823 


65 


— 


1. 116 


*5 


— 


1.850 




170 


1. 150 


— 


30 


1.900 


— 


180 


1. 161 


20 


— 


1.946 


70 


— 


1.200 


— 


40 


1.950 


, — 


190 


1. 210 


25 











520 



ELECTRO-DEPOSITION OF METALS. 



Fig. 155. 



It will be seen that every degree Tvvaddell represents 0.005 
in the specific gravity hydrometer, and every io° represents 
0.050. To convert degrees Baume into readings showing 
direct specific gravity, subtract the readings on Baume's scale 
from the number 144, and divide this by the difference. For 
example, 144 — 66 = Tr = 1.846 , the specific gravity of a 
liquid registering 66° on a Baume hydrometer. Baume has 
one hydrometer for liquids lighter than water (the readings of 
which are given in the first 16 sets of figures in the foregoing 
table), and one for liquids heavier than water. 

Filters. — Filtering a solution, a bath, or any other liquor, 
consists in causing it to pass through a permeable substance, 
the pores or meshes of which are sufficiently 
closed to retain all the undissolved substances,, 
which are thus separated from the liquid part. 
Filters are of very different materials and 
shapes. Cloth, muslin, etc., are coarse filters 
or strainers, made in the form of pockets. 
Their filtering power is considerably improved 
by covering them with a layer of sand, wool, 
boneblack, etc. These latter substances them- 
selves, properly supported, will act as filters. 
Felted wool (generally rabbit's hair) is made in the shape 
of a conical pocket (Fig. 155), but is suited only for neutral 
substances. Alkalies destroy it rapidly. 

Concentrated acids are filtered through amianthus, or asbes- 
tos, compressed in the neck of a glass funnel upon 
broken fragments of glass. 

The most useful filtering material, however, is 

unsized paper. This filter (Fig. 156) is prepared 

by folding diagonally a square piece of porous 

paper, which thus prepared forms a triangle. 

This is again folded in half. Then, beginning at 

one edge, smaller folds are made alternately to the right and 

to the left, but all converging towards the point, like a fan. 

The filter is now partially opened, trimmed on top, and intro- 




Fig. 156. 




CHEMICAL PRODUCTS AND APPARATUS USED. 



521 



Fig. 157. 



duced into the funnel, care being had that all the projecting 
edges rest against it. 

If it be feared that the filter will not resist the weight of the 
liquid, the point is twisted to the left or to the right, and while 
it is still held between two fingers of the left hand, the whole 
filter is inverted, so that the inward folds become 
the outward ones. A filter with such a rounded 
point is better supported in the funnel, and filters 
more rapidly. 

This method is preferable for rapid filtration ; 
but if it is desired to recover precipitates, the 
filter represented by Fig. 157 is more suitable. A circular 
sheet of paper is twice doubled up, and by carefully opening it 
three thicknesses of paper are laid on one side, leaving one 
single thickness on the other side. 

Siphons. — The most simple and handy siphon, in many cases, 
is a piece of lead pipe bent so as to have two unequal branches, 




Fig. 158. 





the smaller of which plunges into the liquid to be drawn off. 
A section of India-rubber tube may be employed for similar 
purposes. 

But as these materials may be chemically acted upon by 



522 ELECTRO-DEPOSITION OF METALS. 

various solutions, glass siphons are used, with or without a 
suction tube (Figs. 158 and 159). 

For siphoning corrosive solutions which cannot be touched 
with the fingers, a siphon with a suction tube is used (Fig. 
158). The shorter leg is plunged into the liquid and the 
longer one closed with the finger or an India-rubber pad 
pressed against it; then, with the mouth, suction should be 
carefully applied at the lateral suction tube until the liquid 
fills the longer leg. 

If there be any danger of inhaling a poisonous vapor, the 
action of the mouth may be replaced by an India-rubber ball 
fastened to the suction tube. The longer branch of the siphon 
is closed as before, and the ball compressed in order to remove 
the air. By its elasticity the ball resumes its former volume, 
thus producing a suction which starts the siphon in action. 

Stirring rods. — These are rods made of various materials, 
and are employed for mixing together liquids or pastes, or 
solids with liquids, or various solids in the dry state. Their 
length and thickness should be suited to the volumes to be 
mixed. 

Suitable stirring rods are those which have no chemical 
action upon the substances "with which they are brought in 
contact; neither should they become impregnated with them. 
Rods of glass, stoneware, or porcelain are decidedly the best. 
Wood and most metals should be avoided, because the former 
is absorbent and the latter are corroded and easily oxidized. 

The operator should always have near at hand a complete 
assortment of glass stirrers of various sizes, and with fused or 
rounded ends, in order not to scratch the vessels in which he 
operates. 



APPENDIX. 



USEFUL TABLES. 



Table of elements with their symbols, atomic weights, and 
specific gravities. 



Name. 



Aluminium 
Antimony . 
Arsenic . . . 
Barium . . . 
Beryl ium . 
Bismuth . . . 
Boron .... 
Bromine . . 
Cadmium . . 
Caesium . . . 
Calcium . . . 
Carbon .... 
Cerium . . . 
Chloride . . 
Chromium. 

Cobalt 

Copper . . . 
Didymium. 
Erbium . . . 
Fluorine . . 

Gold 

Hydrogen . 
Indium . . . 

Iodine 

Iridium . . 

Iron 

Lanthanum 

Lead 

Lithium .. . 
Magnesium 
Manganese 
Mercury . . 



Sym- 


Atomic 


Specific 


bol. 
Al 


weight . 


gravity. 


27.1 


2.67 


Sb 


120.4 


6.72 


As 


75-° 


5.63 


Ba 


1374 


4.00 


Be 


9-3 


2.10 


Bi 


208.11 


9-799 


B 


11.0 


2.68 


Br 


79-95 


2.97 


Cd 


1 1 2.4 


8.67 


Cs 


i33-o 


— 


Ca 


40.1 


3.10 


C 


12.0 


3-5o 


Ce 


139.0 




CI 


35-5 


2.45 


Cr 


52.1 


6.81 


Co 


59.00 


8.50 


Cu 


93-7 


8.88 


D 


95-° 


— 


E 


166.0 


— 


F 


19.0 


— 


Au 


197.2 


19.50 


H 


1.003 


0.069 


In 


1 14.0 


— 


I 


126.85 


4.98 


Ir 


I93-I 


21.15 


Fe 


55-9 


7.70 


La 


138.6 




Pb 


206.92 


n.38 


Li 


7-°3 


o.59 


Mg 


24-3 


1.74 


Mn 


55-o 


8.00 


Hg 


200.0 


13.59 



Name. 



Molybdenum. . 

Nickel 

Niobium 

Nitrogen 

Osmium 

Oxygen 

Palladium 
Phosphorus. . . 

Platinum 

Potassium 
Rhodium . . . . 
Rubidium . . . . 
Ruthenium . . . 

Selenium 

Silicium 

Silver 

Sodium 

Strontium 

Sulphur 

Tantalum . . . . 
Tellurium . . . . 

Thallium 

Thorinum . . . . 

Tin 

Titanium 

Tungsten 

Uranium 

Vanadium. . . . 

Yttrium 

Zinc 

Zirconium . . . . 



Sym- 


Atomic 


bol. 


Weight. 1 
96.0 


Mo 


Ni 


58.7 


Nb 


93-7 


N 


14.04 | 


Os 


191.0 





16.0 


Pd 


107.0 


P 


31.0 


Pt 


194.9 


K 


39.11 


Rh 


103.0 


Rb 


85.4 


Ru 


101.7 


Se 


79.2 


Si 


28.4 


Ag 


107.92 


Na 


23-05 


Sr 


87.60 


S 


32.07 


Ta 


182.8 


Te 


127 


Tl 


204.15 


Th 


232.6 


Sn 


1 19.0 


Ti 


48.15 


W 


184.0 


U 


239.6 


V 


51-4 


Y 


89.0 


Zn 


654 


Zr 


90.4 



8.60 

8.6 

6.67 

0.972 

21.3 
1.088 
1.8 
1.84 

21.15 
8.805 

12.10 
1.50 

11.40 
4.28 

249 
10.50 
0.972 

2.54 
2.045 

10.78 
6.18 

11.86 
7.70 
7.29 
5.30 

18.40 

19.40 
5^o 

7.2 
4.20 



(523) 



524 ELECTRO-DEPOSITION OF METALS. 

Table of chemical and electro-chemical equivalents. 



Name of substance. 



Hydrogen 
Aluminium 
Antimony . 
Arsenic . . , 
Cobalt 
Copper . . . 

Gold 

Iron 

Lead 

Nickel 

Platinum .. 

Silver 

Tin 

Zinc 



Sym- 
bol. 


Specific 
gravity. 


Chemical 
equiva- 
lent. 


H 


j 


j 


Al 


2.6 


13-7 


Sb 


6.8 


122 


As 


5-7 


75 


Co 


8.7 


29-5 


Cu 


8.8 


31.8 


Au 


19.2 


9^3 


Fe 


7-5 


28 


Pb 


"•3 


103.5 


Ni 


8.6 


29-5 


Pt 


21.2 


98.6 


Ag 


10.5 


108 


Sn 


7-3 


32.7 


Zn 


7.2 


59 



Electro- 
chemical equi- 
valent. 
Milligrammes. 



0.01036 
0.14250 
1.26880 
0.78000 
0.30680 
0.33070 
1.02230 
0.29120 
1.07640 
0.30680 
1.02540 
1. 1 2340 
0.34010 
0.61360 



Weights 
decomposed 
by 1 ampere 

in 1 hour. 
In grammes. 



0.0375 
0.5I37 
4-5750 
2.8125 
1. 1062 
1. 1925 
3.6862 
1.0500 
3.8812 
1. 1062 

3-6975 
4.0500 
1.2262 
2.2125 



With the assistance of this table it can be calculated how 
long a measured surface has to remain in the bath in order to 
acquire a deposit of determined weight with the most suitable 
current-density. Suppose the time is to be determined which 
a square decimetre of surface has to remain in the nickel bath 
in order to acquire a deposit of T \ millimetre thick with a cur- 
rent-density of 0.5 ampere. First calculate the weight of the 
deposit by multiplying the surface in square millimetres with 
the thickness and specific gravity. One square decimetre is 
equal to 10,000 square millimetres, which, multiplied by y ¥ mil- 
limetre, gives as a product 1000, which multiplied by the 
specific gravity of nickel — 8.6 — gives 8600 milligrammes =-- 8.6 
grammes. Since, for the regular deposit per square decimetre, 
a current density of 0.5 ampere is required, and 1 ampere de- 
posits, according to the above table, 1.1062 grammes in 1 hour, 
y 2 ampere deposits 0.5331 gramme in 1 hour, and, therefore, 
about 16 hours will be required for the deposition of 8.6 
grammes. 

According to this example, the time, for instance, can also be 
calculated which one, two, or more dozen of knives and forks 



USEFUL TABLES. 



525 



or spoons, which are to have a deposit of silver of a determined 
weight, must remain in the bath when the current-density is 
known. Suppose 50 grammes of silver are to be deposited 
upon 1 dozen of spoons, and the most suitable current density 
is 0.2 ampere per square decimetre ; if the surface of 1 spoon 
represents 1.10 square decimetres, the surface of ] dozen 
spoons of equal size is 13.2 square decimetres. Hence, they 
require 13.2 xO,2 = 2.64 amperes; now, since 1 ampere de- 
posits in one hour 4.05 grammes of silver, 2.64 amperes deposit 
in the same time 10.7 grammes of silver, and with this current 
the dozen spoons must remains about 4^ hours in the bath for 
the deposition of 50 grammes of silver upon this surface. 

Table showing the value of equal current volnmes as expressed 
in amperes per square decimetre, per square foot, and per 
square inch of electrode surface. 



es 

uare 

etre. 




"V 3 


es 

uarc 

etre. 


eres 
uare 


"v s 


es 

quare 

etre. 


u 2 


«3 


Amper 
per sq 
decim 


a- cr 

3 u 
II ^ 


=Amp 
per sq 
inch. 


Amper 
per sq 
dceim 


a, cr 
II ^ 


O. cr 

II ^- s 


j-c <n a 

0-. <u <~> 

< 


ft, cr 
II ^ 


Oh cr 

If S-.S 


0.05 


0.46 


0.0032 


0.8 


743 


0.0516 


6.20 


57-6 


0.4 


0.054 


o-5 


0.0035 


0.86 


8 


0-0555 


6.46 


60 


0.4167 


0.077 


0.72 


0.005 


0.9 


8.36 


0.0581 


7 


65.O 


0.4516 


O.I 


o.93 


0.0064 


0-93 


8.64 


0.06 


7-53 


70 


0.4861 


O.I I 


1 


0.0069 


0.97 


9 


0.0625 


7-75 


72.O 


°-5 


0.15 


1.44 


O.OI 


1 


9.29 


0.0645 


8 


74-3 


0.5161 


0.2 


1.86 


0.0129 


1.08 


10 


0.0694 


8.61 


80 


o-5555 


0.22 


2 


0.0139 


1.09 


10.28 


0.07 


9 


83-6 


0.5806 


0.3 


2.79 


0.0193 


1.24 


11.52 


0.08 


9-3° 


86.4 


0.6 


0.31 


2.88 


0.02 


i-39 


12.96 


0.09 


9.69 


90 


0.6250 


0.32 


3 


0.0208 


r -55 


14.4 


O.I 


10 


92.9 


0.6452 


0.4 


3-7i 


0.0258 


2 


18.6 


0.1290 


10.76 


100 


0.6944 


0.43 


4 


0.0278 


2 -i5 


20 


0.1389 


10.85 


100.8 


0.7 


0.46 


4.32 


0.03 


3 


27.9 


O.I935 


12.40 


115. 2 


0.8 


o-5" 


4.64 


0.0323 


3.10 


28.8 


0.2 


13-95 


129.6 


0.9 


0.54 


5 


0.0348 


3-23 


30 


0.2083 


i5-5o 


144.0 


1 


0.6 


5-57 


.0.0387 


4 


37- 1 


0.2581 


20 


185.8 


1.2903 


0.62 


5.76 


0.04 
0.0417 


4.30 


40 


0.2778 


21.53 


200 


1.3889 


0.65 


6 


4.60 


43-2 


0.3 


30 


278.7 


: -9355 


0.7 


6.50 


0.0452 


5 


46.4 


0.3226 


3 r -o 


288 


2 


o-75 


7 


0.0486 


5.38 


5o 


0.3478 


32.3 


300 


2.0833 


0.77 


7.20 


0.05 


6 


55-7 


0.3871 


46.5 


432.0 


3 



By this table the current-density may be expressed in 



526 



ELECTRO-DEPOSITION OF METALS. 



amperes per square decimetre, square foot, or square inch, any 
of them being given. Thus a current of I ampere per square 
decimetre has the same electrolytic value as one of 9.29 
amperes per square foot, or 0.0645 P er square inch. To find 
the value of intermediate numbers, not shown above, add 
together the various numbers representing the hundreds, ten?, 
units, and decimals of the given quantity. Thus 27.5 amperes 
per square decimetre (= 20 + 7 + 5) are equivalent to 185.8 + 
65+4.64=255.44 amperes per square foot, or 1.2903 + 
0.4516 + 0.0323 = 1.7742 amperes per square inch. 

Table showing the specific electrical resistances* of different sul- 
phuric acid solutions at various temperatures (Feeming 
Jenkin ) . 



Specific 






Temp 


erature (Fahrenheit). 






gravity of 






























acid. 


S2 1 ' 


39.2° 


46. 4 C 

1.04 


53 6° 


60.8° 


68° 


75.2° 


82.4° 


1. 10 


i-37 


1. 17 


c.92 


0.84 


0.79 


0.74 


0.71 


1.20 


i-33 


1. 11 


o-93 


0.79 


0.67 


o-57 


0.49 


0.41 


!- 2 5 


1.31 


i.c 9 . 


0.90 


0.74 


0.62 


0.51 


<M3 


0.36 


1.30 


1.36 


»-i3 


0.94 


0.79 


0.66 


0.56 


0.47 


0.30 


1.40 


1.69 


1.47 


1.30 


1.16 


1.05 


0.96 


0.89 


0.84 


1.50 


2.74 


2.41 


2.13 


1.89 


1.72 


1.61 


1.32 


1.42 


1.60 


4-32 


4.16 


3.62 


3-" 


2-75 


2.46 


2.21 


2.02 


1.70 


9.41 


7.67 


6.25 


5- 12 


4.23 


3-57 


3.07 


2.71 



Table showing the specific electrical resistances* of different copper 
sulphate solutions at various temperatures (Fleeming Jenkin}. 



No. of parts of 
copper sulphate 
dissolved in ioo 
parts of water. 



12 

r6 
20 
24 

28 







Temperat 


ires (Fahrenheit). 






57.2° 


60.8° 


64.4° 


6S C j 75.2° 

! 


82.4° 


86° 


45-7 


43-7 


41.9 


40.2 


37.1 


34-2 


32.9 


3t>-3 


34-9 


33-5 


32.2 


29.9 


27.9 


27.0 


31.2 


30.0 


28.9 


27.9 


26.1 


24.6 


24.0 


28.5 


27-5 


26.5 


25.6 


24.1 


22.7 


22.2 


26.9 


25.9 


24.8 


23-9 


22.2 


20.7 


20.0 


24.7 


23-4 


22.1 


21.0 18.8 


16.9 


16.0 



* By the term " specific resistance," in the above tables, is meant the absolute re- 
sistance in ohms of a column of the liquid i square centimetre in eross-secticn and I 
centimetre long; in other words, it is the resistance of a cubic centimetre of the 
liquid. The diminution of resistance accompanying a rise of temperature should be 
especially marked. 



USEFUL TABLES. 

Table of the electro-motive force of elements. 



527 



Name of element. 


Constitution. 


Electro- 
motive force 
in volts. 


Authority. 


Wollaston 

Smee 

Daniell 


Amalgamated zinc and cop- 
per in dilute sulphuric acid 

(1:12). 

Amalgamated zinc in sulphuric 
acid; platinized silver, or 
platinum in sulphuric acid 

(1:12). 

Amalgamated zinc in sulphuric 
acid (1:14); copper in 
saturated solution of copper 
sulphate. 

Zinc in dilute sulphuric acid 
(1:12); copper as above. 

Zinc in sal ammoniac, carbon 
with manganese peroxide in 
sal ammoniac. 

Zinc in solution of common 
salt; carbon with manga- 
nese peroxide in common 
salt solution. 

Zinc in dilute sulphuric acid 
(1:12); carbon in mercu- 
rous sulphate. 

Zinc in dilute sulphuric acid 
(1 : 12); platinum in fum- 
ing nitric acid. 

Zinc as above; platinum in 
nitric acid of 1.38 sp. gr. 

Zinc as above ; carbon in fum- 
ing nitric acid. 

Zinc as above ; carbon in nitric 
acid of 1.38 sp. gr. 

Zinc as above: carbon in bi- 
chromate of potassium. 

Zinc and carbon in bichromate 
of potassium. 


(0.886 
\ 0.861 
1 0.719 

r 1.098 
1 1. 107 

1 0.541 
ti.192 

r 1.079 

J do. 
1 do. 
[ do. 

f 0.978 
\0.98 

fi.481 

1.561 

I 1^942 

1 1-259 

f 1-493 
\ 1.360 
I1.34 

f 1-524 
J 1-542 
1 1.482 
I 1.440 

1.956 

i 1-524 
I 1.542 

r 1.964 
1 1-95 

r 1.888 

\ 1.941 
{ 1.880 

r 2.028 

\ 1.905 
(2.120 

1.825 


Clark and Sabine. 

Sprague. 

De la Rive. 

Clark and Sabine. 
Sprague. 
De la Rive. 
Naclari. 

Clark and Sabine. 
Sprague. 
De la Rive. 
Naclari. 


do 


Leclanche 

do 


Du Moncel. 

Clark and Sabine. 
Sprague. 
De la Rive. 
Beetz. 

Sprague. 
Naclari. 
Du Moncel. 

Clark and Sabine. 
Sprague. 
Naclari. 
Du Moncel. 


Marie Davy 


do 


Clark and Sabine. 

Clark and Sabine. 
Sprague. 

Clark and Sabine. 
Du Moncel. 

Clark and Sabine. 

Beetz. 

Naclari. 

Clark and Sabine. 

Sprague. 

Naclari. 

Naclari. 




do 


do 


Grenet 





528 ELECTRO-DEPOSITION OF METALS. 

Table showing the solubility of various substances. 



Substances of which I part is soluble 



Alum 

Ammonium carbonate 

Citric acid 

Copper sulphate (blue vitriol) 

Ferric chloride 

Ferrous chloride 

Ferrous sulphate (green vitriol) 

Iodine 

Nickel nitrate 

Nickel sulphate 

Potash 

Potash, caustic 

Potassium cyanide 

Potassium dichromate (red chromate 

of potash) 

Sal ammoniac - 

Silver, citrate 

Silver, nitrate 

Soda 

Soda, caustic 

Sodium bisulphite 

Sodium chloride 

Sodium sulphite 

Yellow prussiate of potash 

Zinc chloride 

Zinc sulphate 



In water 



of59°F. of 212° F. 



6.5 

4.0 

o-75 

5-° 

0.6 

0.8 

i-5 

7000 

2.0 

3.0 

0.9 

0.5 
readily soluble 



3-0 

sparingly 

soluble 

0.8 

1.0 

2.0 
soluble 
2.8 
4.0 
4.0 
o-3 
2.0 



o.3 

decomposes 

0.6 

1-3 

very soluble 
very soluble 

0.3 

soluble 

very soluble 

2.0 

very soluble 

very soluble 

readily soluble 

1.2 
1.4 

sparingly 

soluble 

very soluble 

o.3 

°-5 

soluble 

2.5 
1.0 
1.0 

very soluble 
1.0 



In alcohol of 
59° F. 



insoluble. 

soluble. 

soluble. 

insoluble. 

soluble. 

soluble. 

insoluble. 

readily soluble. 

soluble. 

insoluble. 

insoluble. 

soluble. 

soluble. 

insoluble. 

sparingly 

soluble. 



1 part at a 

boiling heat, 
insoluble, 
insoluble. 



60 

insoluble, 
insoluble. 

insoluble. 



Table Showing the Composition of the Most Usual Alloys and 

Solders. 

Alloys are combinations or mixtures, effected by the fusion 
of two or more different metals in definite proportions. The 
electro plater employs them so constantly that it is important 
that he be acquainted with the composition of the most usual 
alloys, and that he learn the preparation of several of them, 
which, like the fusible alloys of Darcet, will often be serviceable. 

It is, of course, possible to vary ad infinitum the mixtures 
and the proportions of the component metals given in the fol- 



USEFUL TABLES. 



529 



lowing table, and thus to arrive at an unlimited number of 
alloys which, on account of slight differences of color, ductility, 
sonorousness, etc., have received a great variety of names.* 

1. Alloys. 



Argentan, elastic 

Brass for articles worked with the 
hammer 

" for turning 

" for decorating purposes 

" for sheet 

Britannia 



Bronze for bells . . 

" for larger bells. . . . 

" for smaller bells . . 

" for clocks 

" for cymbals 

" for gongs 

" for medals 

" for large ordnance 

" for small ordnance 

" for statues 



Chrysochalk 

Darcet's fusible alloy. 



German silver 



Potin (French yellow brass) . 

Similor 

Talmi gold 

Telescope mirrors (reflectors) . 
Tombac 

" pale 

" red 

" resembling gold 



CL 

a. 

U 



>-. 




fi 










s 


a 






3 




< 


< 



Parts. 



574 25 



70 
66 
60 

75 

4 

10 

80 

78 
42 

75 

80 

100 

ICO 

90 

93 
84 
84 
82 
80 



50 

53 
8 

4 

55 

it.9 
100 

86.6 
100 

80 

76 

88 



30 
32 
40 

25 



11 

10.5 



3-5 
31-25 

3-5 

1 

17 
24.9 

12 
12.6 

20 
24 
12 
16 



70.5 

22 

20 

22 

58 

25 
20 

25 



2.4 

50 



*3 



5 
4 

15.75 - 
3 

1 

23 



25-5 
62 



* For a full description of alloys and amalgams see "The Metallic Alloys," edited 
by W. T. Brannt. Philadelphia. Henry Carey Baird & Co. 1896. 

34 



530 



ELECTRO-DEPOSTTION OF METALS. 



2. Solders. 

a. Soft Solder. 



Tin. 


Lead. 


Melts 
at degrees F. 


Tin. 


Lead. 


Melts 


Parts. 


Parts. 


at degrees F. 




2 5 


558° 


■ i# 


1 


334° 




IO 


54i 


2 


1 


340 




5 


5 11 


3 


1 


356 




3 


482 


4 


1 


365 




2 


44 1 


5 


1 


378 




I 


37° 


6 


1 


381 



b. Hard Solder. 



Very refractory 
t< ti 

Refractory .... 

Readily fusible 

Half white . . . 
n 

White 

a 

Very ductile . • 



Brass. 


Zinc. 


Tin. 






Parts. 






85.42 


12.58 







7 


1 


— 




3 


1 


— 




4 


1 


— 




5 


2 


— 




5 


4 


— 




12 


5 


1 




44 


20 


2 




40 


2 


8 




22 


2 


4 




18 


12 


30 




78.25 


17-25 


— 





c. Silver Solder. 



Brass silver solder 

Hard silver solder 

Very hard solder 

Middling hard solder. . . . 

Soft silver solder 

Silver solder for cast iron 
Silver solder for steel . . . . 



Silver. 


Copper. 


Brass. 


Tin. 


Zinc. 


Parts. 


1 

4 
40 


1 

10 


1 


— 


— 


40 


10 


40 


10 


— 


32 


— 


32 


2 


— 


20 


3° 


— 


— 


10 


30 


10 


— 


— 


— 



USEFUL TABLES, 
d. Gold Solder. 



531 



Hard solder for fineness 750 

Soft " " " 750 

Solder for fineness 583 

" " " 583 

" " «• less than 583 



Gold. 



Silver. J Copper. 



Zinc. 



Parts. 



« (< 



Solder readily fusible 



for yellow gold 10 



•94 




5.01 
1 



Table of the melting-points of some metals. 



Metals. 


Degrees 
Fahrenheit. 


Metals. 


Degrees 
Fahrenheit. 


Tin 


458.6 
599-4 
773-6 
809.6 

1859 
1994 


Gold 


2372 

2912 to 3092 
2912 

3092 to 3452 
3452 to 3812 






Zinc 


Nickel 




Steel 






Copper 





Table of high temperatures. 




Description. 


Degrees 
Fahrenheit. 


Description. 


Degrees 
Fahrenheit. 


Incipient red heat 


977 
980 

1000 
1 140 
1200 
1310 


An orange-red heat 

A bright red heat 

A dull white heat 


I7OO 

1873 
I996 
3OOO 

330O 


A dull red heat visible in 


Heat of a common fire 


Heat of a good blast 


Dull red heat 





Table of the specific gravity and content of solutions of potassium 
carbonate at 5 7. 2° Fahrenheit, according to Gerlach. 



Potassium 




Potassium 




Potassium 




carbonate, 


Specific gravity. 


carbonate, 


Specific gravity. 


carbonate, 


Specific gravity. 


per cent. 




per cent. 




per cent. 




2 


I.OI829 


20 


1. 19286 


38 


I.39476 


4 


I.O3658 


22 


1. 21402 


40 


I.41870 


6 


I.°55I3 


24 


i.235 x 7 


42 


144338 


8 


I.07396 


26 


1. 25681 


44 


I.46807 


IO 


I.O9278 


28 


1.27893 


46 


1 .49314 


12 


I.II238 


30 


1.30105 


48 


I.51861 


14 


I.I3I99 


32 


1-32417 


50 


I.54408 


16 


1. 1 5200 


34 


1.34729 


52 


I.57048 


18 


I. T7243 


36 


1.37082 


52.024 


I.57079 



532 



ELECTRO-DEPOSITION OF METALS. 



Table showing the specific gravity of sulphuric acid at 5p° F., 
according to Kolb. 



6 


>> 


100 parts by 


One litre 


S 


> 


100 parts by 


One litre 


s 




weight 


contains in 


3 


J- 


weight 


contains in 


<l> 

0) 


&J0 


'0 


contain 


kilogrammes. 


PQ 

t/j 

<L> 

1) 

V- 

0J3 
(Li 

Q 
34 



'0 

Oh 


contain 


kilogrammes 


<L> 

Q 


S0 3 . 


H 2 S0 4 . 


so 3 - 


H 2 S0 4 . 


S0 3 . 


H 2 S0 4 . 


S0 3 . 
0.429 


HS0 4 . 


o 


I. ceo 


0.7 


0.9 


0.007 


0.009 


I.308 


32-8 


40.2 


0.526 


i 


1.007 


i-5 


1.9 


0.015 


0.019 


35 


1.320 


33-8 


41.6 


0.447 


o.549 


2 


1.014 


2'3 


2.8 


c.023 


0.028 


36 


1-332 


35- 1 


43-o 


0.468 


o.573 


3 


1.022 


31 


3.8 


0.032 


0.039 


37 


1-345 


36.2 


44-4 


0.487 


o.597 


4 


1.029 


3-9 


4.8 


0.040 


c.049 


38 


1-357 


37-2 


45-5 


0-505 


0.617 


5 


i-°37 


4-7 


*! 


0.049 


0.000 


39 


i-37o 


38.3 


46.9 


0.525 


0.642 


6 


1.045 


5.6 


6.8 


0.059 


0.071 


40 


1.383 


39.5 


48.3 


0.546 


0.668 


7 


1.052 


6.4 


6.8 


0.067 


0.082 


4i 


1-397 


40.7 


49.8 


0.569 


0.696 


8 


1.060 


7.2 


8.8 


0.076 


0.093 


42 


1.410 


41.8 


51.2 


0.589 


0.722 


9 


1.067 


8.0 


9.8 c.085 


0.105 


43 


1.424 


42.9 


52.8 


0.61 1 


0.749 


IO 


*-075 


8.8 


10.8 0.095 


0.116 


44 


1.438 


44.1 


54-o 


0.634 


0.777 


ii 


1.083 


9-7 


1 1.9 0.105 


0.129 


45 


1-453 


45-2 


55-4 


0.657 


0.805 


12 


1. 09 1 


10.6 


13.C 0.1 16 


0.142 


46 


1.468 


46.4 


56-9 


0.681 


0.835 


13 


1. 100 


"•5 


14.1 c.126 


O.I55 


47 


1.483 


47.6 


58.3 


0.706 


0.864 


14 


1. 108 


12.4 


!5- 2 O.I37 


0.168 


48 


1.498 


48.7 


59.6 


0.730 


0.893 


*5 


1.116 


13-2 


16.2 O.I47 


0.181 


49 


1.514 


49-8 


61.0 


0-754 


0.923 


16 


1. 125 


14.1 


I7.3 '0.159 


0.195 


5° 


1-530 


51.0 


62.5 


0.780 


0.956 


17 


1. 134 


J 5-i 


18.5 


0.172 


0.210 


5 1 


1.540 


52.2 


64.0 


0.807 


0.990 


18 


1. 142 


16.0 


19.6 


0183 


0.224 


52 


1-5^3 


53-5 


65.5 


0.836 


1.024 


19 


1. 152 


17.0 


20.8 


0.196 


0.233 


53 


1.580 


54-9 


67.0 


0.867 


1.059 


20 


1. 162 


18.0 


22,2 


0.209 


0.258 


54 


1-597 


56.0 


68.6 


c.894 


1.095 


21 


1.171 


19.0 


23.3 


0.222 


0.273 


55 


1.615 


57- 1 


70.0 


0.922 


1.131 


22 


1. 180 


20.0 


24-5 


0.236 


0.289 


56 


1.634 


58-4 


71.6 


o.954 


1. 170 


23 


1.190 


21. 1 


25.8 


0.25 c 


0.307 


57 


1.652 


59-7 


73-2 


0.986 


1. 210 


24 


1.200 


22.1 


27.1 


0.265 


0.325 


58 


1.672 


61.0 


74-7 


1.019 


1.248 


25 


1. 210 


23.2 


28.4 


0.281 


o.344 


59 


1.691 


62.4 


76.4 


!- 55 


1.292 


26 


1.220 


24.2 


29.6 


0.295 


0.361 


60 


1.711 


63.8 


78.1 


1.092 


1.336 


27 


1.231 


25.3 


31.0 


0.31 1 


0.382 


61 


1-732 


65.2 


79.0 


1. 129 


1.384 


28 


1. 241 


26.3 


32.2 


0.326 


0.400 


5 2 


1-753 


66.7 


8r. 7 


1. 169 


1.432 


29 


1.252 


27-3 


33-4 


0.342 


c.418 


63 


1.774 


68.7 


84.1 


1. 219 


1.492 


30 


1.263 


28.3 


34-7 


o.357 


O.438 ! 


64 


1.796 


70.6 


86.5 


1.268 


1-554 


3i 


1.274 


29.4 


36.0 


o.374 


0.459 


65 


1.819 


73-2 


89.7 


1-332 


1.632 


32 


1.285 


30.5 


3 U 


0.392 


0.481 


66 


1.842 


81.6 


1 00.0 


i-5°3 


1.842 


33 


1.297 


3i.7 


38.8 


0.41 1 


O.503 | 















USEFUL TABLES. 



533 



Table of the specific gravity and content of nitric acid, 
according to Kolb. 



o 

I 

2 

3 

4 
5 
6 

7 

8 

9 
io 

12 

<3 
14 
*5 

16 

17 

18 

19 
20 
21 
22 

23 

24 

25 
26 
27 



Specific 
gravity. 



ice parts con- 
tain at 32° F. 



.OCO 
.C07 
.014 
.022 
.029 
.036 
.044 
.C5 2 
,060 
,067 

•075 
.083 
.C9 1 
.IOO 
,108 
.116 
•125 
.134 

■'43 

.IQ2 
l6l 
.171 

.180 
.190 
.199 
.2IO 
.221 
.231 



HN0 3 . 


N 2 6 . 


O.O 


O.O 


I.I 


0.9 


2.2 


1.9 


3-4 


2.9 


4-5 


3-9 


5-5 


4.7 


6.7 


5-7 


8.0 


6-9 


9-2 


7-9 


10.2 


8.7 


11.4 


9.8 


12.6 


ic.8 


.13.8 


11.8 


15.2 


13.0 


16.4 


14.0 


17.6 


15.1 


18.9 


16.2 


20.2 


^7-3 


21.6 


18.5 


22.9 


19.6 


24.2 


20.7 


2 5.7 


22.0 


27.0 


23.1 


28.5 


24.4 


29.8 


2S-S 


314 


26.9 


33.1 


28.4 


34-6 


29.7 



ico parts con- 
tain at 59 F. 



HN03. 


N 2 B . 


0.2 


O.I 


i-5 


1-3 


2.6 


2.2 


4.0 


34 


5- 1 


4.4 


6,3 


5-4 


7.6 


6.5 


9.0 


7-7 


10.2 


8-7 


1 1.4 


9.8 


12.7 


ic.9 


14.0 


12.0 


"5-3 


I 3« I 


16.8 


14.4 


18.0 


J 5-4 


19.4 


16.6 


20.8 


17.8 


22.2 


1 0.0 


23.6 


20.2 


24.9 


21.3 


26.3 


22.5 


27.8 


23.8 


29.2 


2r.O 


30.7 


26.3 


32.1 


27.S 


33-8 


28.9 


35-5 


30.4 


37-0 


31.7 



s s 


Specific 


£2 3 


gravity. 


Q 




28 


I.242 


29 


1. 252 


30 


1. 261 


31 


1.275 


32 


I.286 


33 


I.298 


34 


1. 3C9 


35 


I.321 


36 


1-334 


37 


1.346 


3* 


1-359 


39 


1.372 


AO 


1.384 


41 


1.398 


42 


1.412 


43 


1.426 


44 


1.440 


45 


1-454 


46 


1.470 


47 


1.485 


48 


1.501 


49 


1.51b 


49-5 


1.524 


49.9 


i-53o 


50.0 


1.532 


50-5 


r.54i 


51.0 


1 549 


5i-5 


1-559 



100 parts con- 100 parts con- 
tain at 32 F. tain at 59° F. 



HN03. 


No0 5 . 


HNO a . 


N 2 G . 


36.2 


31.O 


38.6 


33-* 


37-7 


32.3 


40.2 


34-5 


39-1 


33-5 


41.5 


35-6 


41. 1 


35-2 


43-5 


37-3 


42.6 


36.5 


45 .0 


38.6 


44.4 


38.0 


47-i 


40.4 


46.1 


39-5 


48.6 


41.7 


48.0 


41. 1 


5°- 7 


43.5 


50.0 


42.9 


52.9 


45-3 


5i-9 


44-5 


55-o 


47.1 


54-o 


46.3 


57-3 


49.1 


56.2 


48.2 


59-6 


51.1 


58.4 


50.0 


61.7 


5 ? -9 


60.8 


52.1 


64.5 


55-3 


63.2 


54-2 


6 7-5 


57-9 


66.2 


56-7 


70.6 


60.5 


69.0 


59-1 


74-4 


63.8 


72.2 


61.9 


78.4 


67.2 


76.1 


65.2 


83.0 


71. 1 


80.2 


68.7 


87.1 


74-7 


84.5 


72.4 


92.6 


79-4 


88.4 


7^-8 


96.0 


H2.^ 


90.5 


77.6 


98.0 


84.6 


92.2 


79 -o 


1 00.0 


85.71 


92.7 


79-5 


— 


— 


95-° 


81.4 


— 


— 


97-3 


8^.4 


— 


— 


1 00.0 


85.71 


— 


— 



Table showing the specific gravity of sal ammoniac solutions at 
66.2 F., according to Schiff. 



Content of 




Content of 




Content of 




the solution, 


Specific gravity. 


the solution, 


Specific gravity. 


the solution, 


Specific gravity. 


per cent. 




per cent. 




per cent. 




! 


I.OO29 


II 


I.C322 


21 


I.0606 


2 


I.OO58 


12 


I.0351 


22 


LO633 


3 


I.C087 


13 


I.03S0 


23 


i.c66o 


4 


I.OII6 


14 


I.O409 


24 


1.0687 


5 


I.OI45 


15 


I.O438 


25 


1.0714 


6 


I.OI74 


16 


I.C467 


26 


1. 074 1 


7 


1.0203 


17 


I.0495 


2 l 


1.0768 


8 


1.0233 


18 


I.0523 


28 


1.0794 


9 


1.0263 


19 


!.o55i 


29 


1.0820 


10 


1.0293 


20 


1-0579 


30 


1.0846 



534 



ELECTRO-DEPOSITION OF METALS. 



Table showing the electrical resistance of pure copper wire 
of various diameters. 







Number of 






Number of 


No. of wire, 




feet required 


No. of wire, 




feet required 


Birmingham 


i foot in ohms. 


to give 


Birmingham 


1 foot in ohms. 


to give 


wire gauge. 




resistance 
of 1 ohm. 


wire gauge. 




resistance 
of 1 ohm. 


OOOO 


O.OOOO516 


19358 


17 


O.OO316 


316.I 


OOO 


O.OOO0589 


16964 


18 


O.OO443 


225.5 


OO 


O.OOOO737 


I35 62 


19 


O.O0603 


165.7 


O 


O.OOOO922 


IO857 


20 


O.O0869 


II5.I 


I 


O.OOOII8 


8452.6 


21 


O.OIO4O 


96.2 


2 


O.OOOI32 


7575-1 


22 


O.OI358 


73-6 


3 


O.OOO159 


63OO.I 


23 


O.OI703 


58.7 


4 


O.OOOI88 


53*9-9 


24 


0.02200 


45-5 


5 


0.000220 


4545-9 


25 


0.02661 


37.6 


6 


O.OOO258 


3870-3 


26 


O.03286 


30.4 


7 


O.OOO329 


3043-4 


27 


O.O4159 


24.O 


8 


O.OOO39I 


2557-1 


28 


O.05432 


18.4 


9 


O.OOO486 


2057.7 


29 


O.063OO 


15.9 


IO 


O.OOO593 


1686.5 


30 


O.07393 


13.5 


n 


O.OOO739 


1352.5 


31 


O.I0646 


9.4 


12 


O.OO0896 


1 1 16.0 


32 


Q.I3144 


7-6 


13 


O.OO 1 180 


847.7 


33 


O.16634 


6.0 


14 


O.OOI546 


647.0 


34 


O.21727 


4.6 


15 


O.OO2053 


487.0 


35 


O.42583 


2.4 


16 


O.OO2520 


396.8 


36 


O.66537 


1.5 



Resistance and conductivity of pure copper at different 
temperatures. 



Centigrade 


Resistance. 


Conductivity. 


Centigrade 


Resistance. 


Conductivity. 


temperature. 






temperature. 






o° 


I. OOOOO 


I. OOOOO 


1 6° 


1. 06 1 68 


.94190 


I 


I. OO38 1 


.99624 


17 


I.06563 


.93841 


2 


I.OO756 


.99250 


18 


I.06959 


•93494 


3 


I.OII35 


.98878 


19 


I.07356 


.93148 


4 


I.OI5I5 


.98508 


20 


I.07742 


.92814 


5 


I.O1896 


.98139 


21 


1. 08 1 64 


.92452 


6 


I.02280 


.97771 


22 


I.08553 


.92121 


7 


I.02663 


.97406 


23 


I.08954 


.91782 


8 


I.03048 


.97042 


24 


I.09365 


.9H45 


9 


1-03435 


.96679 


25 


I.O9763 


.9IIIO 


10 


I.03822 


.96319 


26 


I.IOl6l 


.90776 


11 


I.04199 


•95970 


27 


I. IO567 


•90443 


12 


I.04599 


•95603 


28 


I.II972 


.90113 


13 


I.O4990 


.95247 


29 


I.II382 


.89784 


14 


I.O5406 


.94893 


30 


I.II782 


•89457 


15 


I-°5774 


.94541 









USEFUL TABLES. 



535 



Table showing actual diameters in decimal parts of an inch 
corresponding to the numbers of various wire gauges. 



No. of wire 


Roebling. 


Brown & 


Birmingham 


English legal 


Old English 


gauge. 


Sharpe. 


or Stubs. 


standard. 


or London. 


oooooo 


.46 








.464 





coooo 


•43 


— 


— 


•432 


— 


oooo 


•393 


.46 


•454 


•4 


•454 


ooo 


.362 


.40964 


•425 


•372 


•425 


oo 


•331 


.3648 


.380 


.348 


.38 


o 


•307 


•32495 


,340 


•324 


•34 


I 


.283 


.2893 


•3 


•3 


•5 


2 


.263 


•25763 


.284 


.276 


.284 


3 


.244 


.22942 


•259 


.252 


•259 


4 


.225 


.20431 


.238 


.232 


.238 


5 


.207 


.18194 


.22 


.212 


.22 


6 


.192 


.16202 


.203 


.192 


.203 


7 


.177 


.14428 


.18 


.176 


.18 


8 


.162 


.12849 


.165 


.ifc» 


.165 


9 


.148 


•II443 


.148 


.144 


.148 


IO 


•'35 


.10189 


.134 


.128 


•134 


ii 


.120 


.09074 


.12 


.116 


.12 


12 


.105 


.08081 


.109 


.104 


.109 


*3 


.092 


.07196 


•095 


.092 


•095 


14 


.08 


.06408 


.083 


.08 


.083 


J 5 


.072 


.05706 


.072 


.072 


.072 


1 6 


.063 


.05082 


.065 


.064 


.065 


*7 


.054 


.04525 


.058 


.056 


.058 


18 


.047 


.0403 


.049 


.048 


•049 


19 


.041 


.03589 


.042 


.04 


.04 


20 


•035 


.03196 


•035 


.036 


•035 


21 


.032 


.02846 


.032 


.032 


•0315 


22 


.028 


•02534 


.028 


.028 


.0295 


23 


.025 


.02257 


.025 


.024 


.027 


24 


.023 


.0201 


.022 


.022 


.025 


25 


.C2 


•OI79 


.02 


.02 


.023 


26 


.Ol8 


.01594 


.018 


.018 


•0205 


27 


.017 


.01419 


.016 


.0164 


.01875 


28 


.Ol6 


.01264 


.014 


.0148 


•0165 


29 


.OI5 


.01125 


.013 


.0136 


•oi55 


30 


.OI4 


.01002 


.012 


.0124 


•OI375 


3i 


•°I35 


.00893 


.010 


.0116 


.01225 


32 


•OI3 


.00795 


.009 


.0108 


.01125 


33 


.Oil 


.00708 


.008 


.01 


.01025 


34 


•OI 


.0063 


.007 


.0092 


.0095 


35 


.OO95 


.00561 


.005 


.0084 


.009 


36 


.OO9 


.005 


.004 


.0076 


.0075 



536 



ELECTRO-DEPOSITION OF METALS. 



Weight of iron, copper, and brass wire and plates. 

(Diameters and thickness determined by American gauge.) 



No. of 


Size of 


gauge. 


each 

No. 




Inch. 


oooo 


.46000 


ooo 


.40964 


CO 


.36480 


o 


.32486 


I 


.28930 


2 


•25763 


3 


.22942 


4 


.20431 


5 


.18194 


6 


.16202 


7 


.14428 


8 


.12849 


9 


.11443 


IO 


.10189 


ii 


.000742 


12 


.080808 


13 


.071961 


14 


.064084 


15 


.057068 


16 


.050820 


17 
18 


•045257 


■040303 


*9 


.035890 


20 


.031961 


21 


.028462 


22 


•025347 


23 


.022571 


24 


.020100 


25 


.017900 


26 


.OI594I 


27 


.OI4195 


28 


.OI264I 


29 


.OII257 


30 


.OIOO25 


31 


.O08928 


32 


. 0079^0 


33 


.OO7080 


34 


.O06304 


35 


.OO5614 


36 


.OO50OO 


37 


.C04453 


38 


.OO3965 


39 


•O0553I 


40 


.OO3I44 


Specific | 
Weight p 


;rav 

er 


cubic f 


JOt 



Weight of wire per 1000 
lineal feet. 



Wro't 
iron. 


Steel. 


Copper. 


Brass. 


Lbs. 


Lbs. 


Lbs. 


Lbs. 


560.74 
444.68 
352.66 
279.67 


566.03 
448.88 

355-99 
282.30 


640.51 
507-95 
402.83 
3I9-45 


605.18 

479-9 1 
380.67 
301.82 


221.79 
175-89 
139.48 
110.62 
87.720 


223.89 
177-55 
140.80 
111.66 
88.548 


253-34 
200.91 
159-32 
126.35 
100.20 


239-35 
189.82 
T50.52 
119.38 
94.666 


69-565 
55-165 
43-751 
34.699 
27.512 


70.221 
55-685 
44.164 
35 026 
27.772 


70.462 
63.013 
49.976 
39.636 
31.426 


75-C75 

59-545 
47.219 

37-437 
29.687 


21.820 
17-304 
13.722 
10.886 
8.631 


22.026 
17.468 
13.851 
10.989 
8.712 


24.924 

19.766 
I5-674 
12.435 
9-859 


23-540 
18.676 
14.809 
11.746 
9-3I5 


6.845 
5-427 
4-304 
3-413 
2.708 


6.909 
5.478 
4-344 
3-445 
2-734 


7.819 
6.199 
4.916 
3-899 
3-094 


7.587 
5.857 
4-645 
5.684 
2.920 


2.147 
i-7°3 
i-35o 
1. 071 
0.8491 


2.167 
1. 719 
1-363 
1.081 
0.8571 


2.452 

1 945 
1.542 
1.223 
.9699 


2.317 
1.838 
1-457 
1. 155 
0.9163 


0.6734 

°-5?4° 
0.4235 
0.33^8 
0.2663 


0.6797 
0-539 1 
0.4275 
3389 
0.2688 


.7692 
.6099 
•4837 
.3835 
.3042 


0.7267 
0.5763 
0.4570 
0.3624 
0.2874 


0.2113 

0.1675 
0.1328 
0.1053 
0.08366 


0.2132 
0.1691 
0.1341 
0.1063 
0.08445 


•2413 
•i9 T 3 
•1517 
.1204. 
.0956 


0.2280 
o.i8c8 
O.I434 
0.1137 
0.1015 


.06625 
.05255 
.04166 
•03305 
.02620 


.06687 
•05304 
.04205 
.03336 
.02644 


•o757 

.06003 

.04758 

•03755 

.02992 


•0715 

.05671 

.04496 

.03566 

.02827 


7-7747 


7.847 


8.880 


8.336 


185.874 


90.45 


554.988 


524.16 



Weight of plates per 
square foot. 



Wro't 
iron. 


Steel. 


Copper. 


Brass. 


Lbs. 


Lbs. 


Lbs. 


Lbs. 


17-25 
15-3615 
13.68 
12.1823 


17.48 
15-5663 
13.8624 
12.3447 


20.838 
18.557 
16.525 
14.716 


19.688 
17-533 
15613 
13.904 


10.8488 
9.6611 
8.6033 
7.6616 
6.8228 


10.9Q34 
9.7899 
8.7180 
7.7638 
6.9137 


13.105 
11. 671 
10.393 
9-2552 
8.2419 


12.382 
11.027 
9.8192 
8-7445 
7.787 


6.0758 
5-4105 
4.8184 
4.2911 
3.8209 


6.1568 
5.4826 
4.8826 
4.3+83 
3-8718 


7-3395 
6-5359 
5.8206 
5-i8 3 7 
4.6156 


6-9345 
6.1752 

5-4994 
4 8976 
4.3609 


3.4028 
3.0303 
2.6985 
2.4032 
2.1401 


3.4482 
30707 
2-7345 
2.43" 
2.1686 


4. 1 106 
3 .66c6 
3-2598 
2.9030 
2.5852 


3.8838 
3-4586 
3-0799 
2.7428 
2.4425 


1.9058 
1.6971 
1.5114 
1-3459 
1.1985 


1. 9312 
t.7198 
I-53I5 
1.3638 
1. 2145 


2.3021 
2.0501 
1.8257 
1.6258 
1.4478 


2.1751 
1.937 
1.725 
1. 536i 
1.3679 


1.0673 
•95051 
.84641 
•75375 
.67125 


1.0816 
.96319 
.8577 
.7638 
.6802 


1.28Q3 
1. 1482 
1.0225 
.91053 
.81087 


1. 2182 

1.0849 

.96604 

.86028 

.7661a 


•59775 
•53231 
.47404 
.42214 
•37594 


.60572 
•5394* 
.48036 
.42777 
.38092 


.72208 
■64303 
•57264 
.50994 
•45413 


.68223 
.60755 
.54103 
.48180 
.42907 


.3348 

.29813 

•2655 

.2364 

.21053 


.33926 

.3021 

.26904 

•23955 

•21333 


•40444 
.36014 
.32072 
•28557 
•25431 


.38212 
.34026 
.30302 
.26981 
.24028 


•1875 

.16699 

.14869 

.13241 

.1179 


.16921 
.15067 
.13418 
.11947 


.2265 

.20172 

.17961 

•15995 

.14242 


.2140 

.19059 

•16973 

.15" 

.13456 


7.200 


7 .r 9 6 


8.698 


8.218 


45o. 


456. 


543-6 


513-6 



USEFUL TABLES. 53^ 

Rules for Speed. 

To find speed of counter-shaft in accordance with main shaft 
and machine. — Subtract the number of revolutions on the main 
shaft from the number of revolutions the machine should make ; 
divide the remainder by two. The quotient will show the 
number of revolutions of the counter-shaft. 

Example. — The main shaft runs 200 revolutions per minute, 
while the machine should run 1000 revolutions per minute. 
Deduct 200 from 1000, leaving 800, which divide by 2 ; the 
quotient will then be 400, which is the number of revolutions 
the connter-shaft should make. 

To find diameter of pulley on the main shaft. — Multiply the 
diameter in inches of the receiving pulley of the counter-shaft 
by the number of revolutions the counter-shaft should make 
aud divide the product by the number of revolutions the main 
shaft makes. 

Example. — The counter-shaft makes 400 revolutions, the 
receiving pulley is 75^ inches in diameter, and the main shaft 
makes 200 revolutions; 400 times 7^ equals 3000, which 
divided by 200 equals 15 ; this is the diameter in inches of the 
pulley on the main shaft. 

To find diameter of pulley on counter-shaft carrying belt to 
machine. — Multiply the number of revolutions the machine 
should make by the diameter of pulley of the machine, and 
divide by the number of revolutions the counter-shaft makes. 

Example. — Say the machine should make 1000 revolutions, 
the diameter of pulley on machine being 6 inches, and the 
counter-shaft making 400 revolutions; then multiplying 1000 
by 6 equals 6000; dividing this by 400 gives 15, which should 
be the diameter of the pulley carrying belt from counter-shaft 
to machine. 

To find the speed of a machine. — Multiply the number of 
revolutions of the main shaft by the diameter of pulley in 
inches, and divide by the diameter of receiving pulley of the 
counter-shaft. The result is the speed of the counter-shaft. 



53§ ELECTRO-DEPOSITION OF METALS. 

Then multiply the number of revolutions of counter-shaft by 
diameter of transmitting pulley, and divide by diameter of 
pulley on machine. The result will be the speed of the 
machine. It should be well understood that no other pulleys 
but those in contact with one belt should be considered. 

Comparison of the Scales of the Fahrenheit, Centigrade, and 
Reaumur Thermometers, and Rules for Converting one Scale 
into another. 

These three thermometers are graduated so that the range of 
temperature between the freezing and boiling points of water is 
divided by Fahrenheit's scale into 180 (from 32 to 212 ), 
by the Centigrade into 100 (from o° to ioo°), and by that of 
Reaumur into 80 (from 0° to 8o°) portions or degrees. 

The spaces occupied by a degree of each scale are conse- 
quently as \, i, and * respectively, or as i, 1.8, and 2.25 ; and 
the number of degrees denoting the same temperature, by the 
three scales, when reduced to a common point of departure by 
subtracting 32 from Fahrenheit's, are as 9, 5, and 4. Hence, 
we derive the following equivalents: — 

A degree of Fahrenheit's is equal to 0.5 of the Centigrade or 
to 0.4 of Reaumur's; a degree of Centigrade is equal to 1.8 
of Fahrenheit's or to 0.8 of Reaumur's; and a degree of 
Reaumur's is equal to 2.25 of Fahrenheit's, or to 1.25 of the 
Centigrade. 

To convert degrees of Fahrenheit into the Centigrade or 
Reaumur's, subtract 32 and multiply the remainder by f for 
the Centigrade or f for Reaumur's. 

To convert degrees of the Ceutigrade or Reaumur's into 
Fahrenheit's, multiply the Centigrade by \ , or Reaumur's by f , 
as the case may be, and add 32 to the product. 



INDEX. 



ACCUMULATOR, common form 
of, 91 
plant, installed by Electro- 
Chemical Storage Battery 
Co., 91, 92 
Accumulators, 87-92 
capacity of, 89 
chemical processes which take 

place in, 89 
gal vano- plastic deposition with, 
438, 439 
Acid copper baths, examination of, 
425-427 
free, determination of, in the acid 

copper bath, 425 
potassium carbonate, 507 
regaining of, from exhausted 
dipping baths, 168, 169 
Acids, determination of, in nickel 
baths 249, 250 
organic, salts of, 516, 517 
used in electro-plating, 493-497 
Alexander's process of zincking, 391 
Alkalies and alkaline earths, 497, 498 

poisoning by, 491 
Alkaline platinate bath, 377 
Alliance machine, 7, 8 
Alloys, metallic, first deposition of, 6 
for moulds, 452 
table of, 529 
Alternating current machines, 69 

currents, 25 
Aluminium baths; 408, 409 
deposition of, 407-411 
electro-deposition upon, 409-411 
properties of, 407, 408 
Amalgam of gold, preparation of, 367 
Amalgamating, 309 
Amalgamation of the zinc, 36, 37 
Ammeter, Weston, 121, 122 
Ammeters, 118-123 
Ammonia, 497, 498 
Ammonium alum, 510 
chloride, 500 
hydrate, 497, 498 
phosphate, 515 
potassium sulphate, 509, 510 
' sulphate, 509 



Ampere's theory of magnetism, 11, 12 
Ampere, the, 34 

hours, 89 
Analysis, electrolytic, 253-255 
gravimetric, 251, 252 
volumetric, 252, 253 
Anions, 26, 28 
Anode, 26 
wire, 109 

main and main object wire, 
coupling of the, with the 
resistance boards, volt- 
meter, switch and baths, 
123, 124 
Anodes, arrangement of, 112-114 

carbon, use of, in gold-plating, 

348 
choice of, 182, 183 
for brassing, 287 

copper plating, 268 
galvanoplastic baths, 424, 425 
insolnble, 199 

platinum, 299, 300 
mode of suspending the, 113, 114 
nickel, 198-202 
platinum, use of, in gold-plating, 

348 
silver, 298 
steel, use of, in gold-plating, 346- 

348 
unequal wear of, 177 
Antimony and arsenic, deposits of, 
by contact and immersion, 407 
arsenic, aluminium, deposition 

of, 404-411 
baths, 404, 405 
deposition of, 404, 405 
potassium tartrate, 516 
properties of, 404 
sulphide, 499 
trichloride, 500 
Antique silvering, 331, 332 
Apparatus and instruments, various, 

517-522 
Aqua fortis, 494 
Areas silver-plating, 306-308 
Argentiferous pastes, 326 
Argol, 516 



( 539) 



540 



INDEX. 



Armature, 67 

drum, Hefner-Altenbeck's, 74 

Gramme, 70 
Arsenic, 496 

and antimony, deposits of, by 
contact and immersion, 407 

baths, 406 

deposition of, 405-407 

deposits, defective, cause of, 407 

poisoning by, 491 

properties of, 405, 406 

trisulphide, 499, 500 
Arsenious acid, 496 

addition of, to brass 
baths, 282 

chloride, 501 

sulphide, 499, 500 
Astatic galvanometer, 22 
Atoms, 26 
Auric ch'oride, 503 
Australian patent for directly silver- 
plating iron and steel, 316 

BACCO'S copper bath, 273 
Backing metal, 442 
Backing the deposit or shell, 440-442 
Baking powder, 508 
Balance, plating, 312-314 
Balloons, glass, 517 
Barium cyanide, determination of 

quantity of, 336 
Baskets, dipping, 212, 213 
Bath, bright-dipping, 163, 164 

electro-plating, requisites of a, 

184 
for galvanoplasty in gold, 467 

silver, 467 
lasting qualities of the, 182 
Baths, agitation of, 177, 178 
aluminium, 408, 409 
antimony, 404, 405 
arsenic, 406 
boiling of, 181 
boric acid as an addition to, 188, 

189 
brass, 281-286 
bronze, 292, 293 
cobalt, 256, 257 
concentration of, 175 
copper, 261-267 

copper, for galvauo-plastic depo- 
sitions with a separate source 
of current, 420, 421 
estimation of the condition of, by 

the hydrometer, 175, 176 
for galvanoplasty in iron, 464 
silvering by immersion, 320, 
321 



Baths, gold, 341-346 
heating of, 94, 95 
iron, 400-402 
lead, 397 
nickel, 187-198 
palladium, 382 
platinum, 375-379 
purity of the chemicals for the, 

174 
steel, 400-402 
stirring up the, 176 
suspension of objects in the, 204, 

205 
temperature of, 180, 181 
tin, 383-386 
vats for heating, 112 
Batteries, bichromate, 56 

plunge, 56 
Battery, Cruikshank's trough, 2, 3 
Foote's pinnacle gravity, 4Q, 47 
galvanoplastic depositions with 

the, 419, 420 
trough, 35 
Baume" hydrometer, 519 
Beardslee, G. W., cobalt solution re- 
commended by, 258 
Beeswax, moulding in, 431 
Bell metal, 280 
Belt strapping attachment or endless 

belt machine, 153, 154 
Benzine, removal of grease with, 170, 

171 
Bertrand's aluminium bath, 408 

palladium bath, 382 
Bicarbonate of potash, 507 

of soda, 508 
Bichromate batteries, 56 
battery, Fein's, 58, 57 

Keiser and Schmidt's, 57 
element, 58 
Bicycle spokes, plating apparatus for, 

216, 217 
Binding posts and screws, 113 
Bird, production of the amalgams of 

potassium and sodium by, 4 
Bisulphide of carbon, 499 

addition of, to nickel 
baths, 
196 
to silver 
baths, 
304,305 
Bivalent anions, 28 

kations, 28 
Black color, lustrous, on iron, 482 
upon copper, 471,472 
-lead, gilt or silvered, 434 
-leading machines, 432, 433 



INDEX. 



541 



Black-leading moulds, 431-434 
wet method of, 433, 434 
lustrous, on brass, 474, 475 
sulphide of antimony, 499 
Blue-black color on copper, 471 
color on iron, 483 
steel, 483 
copperas, 510, 511 
-gray color on copper, 471 
vitriol, 510, 511 

table of approximate content 
of, in solutions at different 
degrees Be, 417, 418 
Bobs, cloth, 149 

construction of, 222, 223 
polishing, 148, 149 
Boiling pans, 181 

Boric acid as an addition to baths, 188, 
189 
determination of, 250 
or boracic acid, 495, 496 
Bossard mechano-elec tropl ati ng 

tanks, 178-180 
Bottger on the deposition of nickel 

from its double salt, 6 
Bottger's iron bath, 400 
platinum bath, 375 
tinning solution, 388 
Bouant's method of amalgamation, 37 
Brass and bronzes, coloring of, 474- 
479 
articles, cobalt bath for, 258, 259 
en masse, brown color on, 477 
silvered, spurious gilding of, 

478 
small, tinning solution for, 
388 
baths, 281-286 

examination of, 290 
bronze, Barb£dienne on, 476 
brown color on, 476 
castings, grinding of, 148 
cleansing of, 171 
coating of, with a bright layer of 

zinc, 395 
color resembling gold on, 475, 476 
coloring, Ebermayer's experi- 
ments in, 478, 479 
corn-flower blue on, 477, 478 
dark red brown color on, 477 
deposition of, 280-292 
deposits, polishing of, 160 
gray color with a bluish tinge on, 

475 
lustrous black on, 474, 475 

colors on, 478 
nickel bath for, 195 
nickeling of, 203 



Brass, uiel upon, 331 

pale gold color on, 475 

pickling of, 163 

potassium cyanide as a pickle for, 

164 
preparation of, for silver-plating, 

308, 309 
scratch-brushing of, 157 
sheets, nickeling of, 236, 237 

treatment of, 148 
steel-gray on, 475 
straw color to brown, through 
golden-yellow and tombac 
color on, 475 
varieties of, 280 
various colors upon, 473, 474 
violet color on, 477, 478 
wire and plates, table of weight 
of, 536 
Brassed iron, brown -black color on, 
476 
zinc, brown-black color on, 476 
Brassing, anodes used for, 287 
by contact and dipping, 289 
distance of the objects from the 

anodes in, 289 
execution of, 286-289 
small articles, bath for, 285, 286 
Bright dipping bath, 163, 164 

plating, preparations for silver 

baths, 304. 305 
Platinum Plating Co., platinum 
bath patented by, 375 
Britannia, cleansing of, 171 
nickeling of, 203 
ware, preparation of, for plating, 
318 
silver-plating of, 316, 317 
Bronze articles, clay-yellow color on, 
476, 477 
dark brown color on, 476, 

477 
dead-yellow color on, 476, 
477 
Bronze Barbedienne on brass, 476 
baths, 292, 293 
cleansing of, 171 
deposition of, 292, 293 
pickling of, 163 
Bronzes, 280 

and brass, coloring of, 474-479 
Bronzing, execution of, 293 

on zinc, 481 
Brown-black color on brassed iron, 476 

zinc, 476 
color, dark, on bronze articles, 
476, 477 
upon brass, 476 



542 



INDEX. 



Brown color upon articles en masse, 
477 
copper, 470, 471 
Brugnatelli, first practical results in 

electro-gilding attained by, 3 
Brush- coppering, 273 
Brushes, 136 

management of the, 116 
Buffing, flexible shafts for, 154, 155 
Bunsen element, 40-46 

location of, 43, 44 
elements, manipulation of, 45, 46 
plunge battery, 56 
Burnishers, 160, 161 
Burnishing, 156, 160, 161 

machines, 315 
Burnt lime, 498 

Busts, galvanoplastic reproduction of, 
449-455 
moulding of, 450, 451 
Butter of antimony, 500 
zinc, 501 

CALCIUM carbonate, 508 
hydrate, 498 
Capsules, evaporating, 517, 518 
Carbon, anodes, use of, in gold- 
plating, 348 
artificial, 40, 41 

bisulphide of, addition of, to 
nickel baths, 
196 
addition of, to 
silver baths, 
304, 305 
disulphide or bisulphide, 499 
gas, 41, 42 
Carbonates, 507-509 
Carboy rocker, steel spring, 172 
Cast iron articles, pickling of; 162 
bath for brassing, 284, 285 

zincking, 392 
solution for coating with 

bronze, 292 
tin bath for, 384 
Casting and melting table, 439, 440 
Cathode, 26 
Caustic potash, 497 

soda, 497 
Cell- apparatus, 414-416 

copper bath for, 417 
French form of, 416, 417 
galvanoplastic deposi- 
tion in the, 413-418 
German form of, 417 
large, 416, 417 
Cellulose lacquers and varnishes, 487, 
488 



Centigrade, Reaumur and Fahren- 
heit thermometers, comparison of 
the scales of, and rules for convert- 
ing one scale into another, 538 
Chain, galvanic, 16 
Chains, plating apparatus for, 216 
Chalk, 508 

Chemical action of the electric cur- 
rent, 25-33 
and electro-chemical equiva- 
lents, table of, 524, 525 
products, 493-517 

and various apparatus and 
instruments used in electro- 
plating, 493-522 
treatment of metallic articles, 
161-172 
Chemicals for the baths, purity of, 

174 
Chile saltpetre, 514 
Chloride of zinc, qualities of, 174 
Chlorine combinations, 500-504 

poisoning by, 492 
Chromic acid, 496 
Chromium combination for Bunsen 

cells, 44, 45 
Circuit, closed, 16 
Circular scratch brush, construction 

of a, 135, 136 
Citric acid, 495 

determination of, 250 
Clamond's thermo-electric pile, 61 , 62 
Clausius's theory of the molecules, 

26, 27 
Clay, metallization of, 463 
Cliches, nickeling of, 242-244 
Clock cases of iron and steel, dead 

black coating on, 483 
Closed circuit, 16 
Cloth bobs, 149 
Cobalt bath, Daub's, 258, 259 
Cobalt baths, 256, 257 
carbonate, 509 
chloride, 502 
deposition of, 256-260 
properties of, 256 
solution, Beardslee's, 258 

Warren's, 258 
sulphate, 513 
Cobalting by contact, 259, 260 
Coins, dies for, production of, 448, 

449 
Colcothar, 155 

Cold gilding, baths for, 342-344 
Collecting brushes, 67 
Collector, 67 

Coloring of brass and bronzes, 474- 
479 



INDEX. 



543 



Coloring of copper, 469-474 
iron, 481-484 
tin, 484 
zinc, 479-481 
patinizing, oxidizing, etc., of 
metals, 469-488 
Colors, iridescent, 4, 397-399 
Common salt, 500 
Commutator, 67 
cylinder, 67 

management of the, 116 
Conducting power of metals, 17 
salts, 187, 188 

wires, calculating the thickness 
of, for dynamos, 129, 131 
insulation of, 109 
Conductors, bad, 13' 

good, 13 
Constant elements, 38 
Contact electricity, discovery of, 1 
Continuous current machines, 69 
Copper acetate. 516, 517 

alloys, silvering articles of, 323- 

325 
articles, cobalt bath for, 258, 259 
gilded, stripping of, 371 
scouring and pickling of, 269 
silvered, stripping of, 333 
small, tinning solution for, 
388 
bath for the cell-apparatus, 417 
removal of excess of acid 
from, 418 
baths, 261-267 

acid, examination of, 425- 

427 
containing potassium cya- 
nide, examination of, 274- 
280 
for gal vanoplastic depositions 
with a separate source of 
current, 420, 421 
galvanoplastic, contrivances 
for the agitation of, 423, 
424 
without potassium cyanide, 

266 
wooden vats lined with lead 
for, 110, 111 
black color on, 471 
blue-back color on, 471 
blue-gray color on, 471 
brass and bronze, deposition of, 

261-293 
brown color upon, 470, 471 
carbonate, 508 
castings, grinding of, 148 
chemically pure, 412 



Copper chloride, 501 
cleansing of, 171 
coating of, with a bright layer of 

zinc, 395 
coloring of, 469-474 
current density for nickeling, 206 
cyanides, 505, 506 
deposit of, upon porcelain, pot- 
tery, stoneware, etc., 463 
deposition of, 261-280 
deposits, polishing of, 160, 270, 271 
determination of quantity of, dis- 
solved in stripping cobalted 
copper plates, 257, 25S 
electrolytic determination of, in 

the acid copper bath, 426, 427 
in brass baths, determination of, 

290 
in copper baths, determination of, 
by electrolysis, 277; 
278 
volumetric determin- 
ation of, 278-280 
matt-black on, 471, 472 
nickel bath for, 195 
nickeling of, 203 
pickling of, 163 
plates, cobalting of, 257, 258 
-plating, anodes used in, 268 
execution of, 267-272 
prevention of the formation 
of stains in, 270 
preparation of, for silver-plating, 

308, 309 
printing plates, galvanoplastic 
bath for, 421 
steeling of, 400,401 
properties of, 261 
pure, table of resistance and con- 
ductivity of, 534 
red-brown color on, 471 
reduction of, from its solution by 

iron, early knowledge of, 1 
salts, poisoning by, 491 
scratch-brushing of, 157 
sheet, treatment of, 148 
sheets, nickeling of, 236, 237 
silvering of, early knowledge of, 1 
steel-gray color upon, 473 
sulphate, 510, 511 

solutions, table of specific 
electrical resistances of, 526 
sulphite, baths with, 265 
tubes, production of, by galvano- 
plastic deposition, 460, 461 
various colors upon, 473, 474 
volumetric determination of, in 
the acid copper bath, 425, 426 



544 



INDEX. 



Copper wire and plates, table of 
weight of, 536 
fine, silvering of, 329 
pure, table of electrical 
resistance of, 534 
-zinc alloy, solutions for transfer- 
ring any, 285 
Copperas, 510 

blue, 510, 511 
Coppered art-castings, inlaying of, 
274 
articles, coating of, with another 
metal, 271 
Coppering by contact and dipping, 
272, 278 
small articles en masse, 272 
Cork wheels, 143 

Corn-flower blue on brass, 477, 478 
Corvin's niello, 461 
Coulomb, the, 34 
Coulomb's law, 15 
Counter-current, 27, 210, 211 

shaft, to find speed of, in accord- 
ance with main shaft, 537 
Cream of tartar, 516 
Crucibles, 518 
Cruikshauk's investigations, 3 

trough battery, 2, 3 
Cubic nitre, 514 
Cuivre fume, 471 
Cupric cyanide, 505, 506 

sulphate, 510, 511 
Cupron, copper bath with, 265 

element, 53, 54 
Cuprous cyanide, 505, 506 

sulphite, 511 
Cups, gilding of, 352 
Current-carrying wire, size of, 108 
counter, 27, 210, 211 
density for silvering, 100 
electric, chemical action of, 25-33 
galvanic, 16 
hydro electric, 16 
induced, 24 
inductive, 24 
polarizing, 27, 210, 211 

formation of, 30 
primary, 24 
quantity of, 17-21 

coupling the elements 
for, 20 
regulator, 101-103 
secondary, 24 
services of, 35-92 
volumes, equal, table of value of, 
525, 526 
Currents, alternating, 25 
extra, 25 



Cutlery, preparation of, for plating, 

318 
Cyanides, 504-507 

poisoning by, 490, 491 

DA.NIELD element, 38, 39 
Daub's cobalt bath, 258, 259 
Davy, Sir H., discovery of the metals 

potassium and sodium by, 3 
Deposit, backing the, 440-442 
formation of the, 132, 133 
penetration of the, into the basis- 
metal, 183 
Deposition, galvanoplastic, by the 
battery and dyna- 
mo, 418-425 
in the cell appara- 
tus, 413-418 
of aluminium, 407-411 
antimony, 404, 405 

arsenic, aluminium, 404- 
411 
arsenic, 405-407 
brass, 280-292 
bronze, 292, 293 
cobalt, 256-260 
copper, 261-280 

brass and bronze, 261-293 
iridium, 382 
iron, 399-403 
gold, 339-374 
lead, 396-399 
nickel, 186-256 

and cobalt, 186-260 
palladium, 381, 382 
platinum, 375-381 

and palladium, 375-382 
rhodium, 382 
silver, 294-339 
tin, 383-390 

zinc, lead and iron, 383-403 
zinc, 390-396 
Deposits, polishing of, 160, 161 
De Ruolz, first deposition of metallic 

alloys by, 6 
Dies for coins, reliefs, etc. , production 

of, 448, 449 
Dip-lacquers, 487, 488 
Dipping, 115 

and pickling, 162-164 
baskets, 212, 213 

baths, exhausted, regaining of 
acid and metal from, 168, 169 
Dishes, evaporating, 517, 518 
Doctor, the, 245 
Double fluid hypothesis of electricity, 

14 
Drinking cups, gilding of, 352 



INDEX. 



545 



Drum armature, Hefuer-Alteubeck's, 

74 
Du Fresne's method of gilding, 370, 

371 
Dun's potash element, 54, 55 
Dupr6's solution for Bunsen cells, 44 
Dynamo- and magneto-electric ma- 
chines, 65-87 
data for ordering a, 87-92 
-electric machine, definition of a, 
67 
parts of a, 67 
-electrical machines, American 
types, 9 
European types, 9 
Fein's, 73, 74 

first application of the term, 67 
for plating purposes, evolution of 
the, in the United States, 80-82 
galvanoplastic deposition with 

the, 420-425 
generator, parts of a, 67 
Gramme, 70, 71 
Krottlinger's, 76, 77 
Hansen & Van Winkle Co.'s, 82- 

85 
Lahmever's, 77-79 
Langbem & Co.'s, 79, 80 
"Little Wonder," 81 
rheostat, location of, 118 
rules for setting up and running 

a, 115-117 
Schuckert's, 72, 73 
Weston, 81 
with auxiliary apparatus, scheme 

of a, 1J8 
"Wonder," 81, 82 
Dynamos, arrangement with, 115-131 
calculating the thickness of con- 
ducting wires for, 129, 131 
various constructions of, 86 
Dyne, 33 

EBERMAYER'S experiments in 
coloring brass, 478, 479 
silver immersion bath, 323 
Elbs's theory of the accumulator, 89 
Electric connection gripper, 435 

current, chemical action of, 25-33 
currents, attraction and repulsion 

of, 23 
generators, classes of, 69 
induction, discovery of, 4 
potential, 16 
units, 33, 34 
Electricities, attraction and repulsion 

of, 13 
Electricity, 12-34 

35 



Electricity and magnetism, 10-12 
double fluid hypothesis of, 14 
kinds of, 13 

single fluid hypothesis of, 14, 15 
Electro-chemical equivalents, 32, 33 
Storage Battery Co., ac- 
cumulator plant in- 
stalled by the, 91, 92 
■ chromy, 397-399 
deposition and fire-gilding, com- 
bination of, 369-371 
by contact, 184, 185 
first requisite for the re- 
sult of the process of, 99, 
100 
of iron, -principal use of, 

399 
processes of, 173-185 
depositions upon aluminium, 409- 

411 
etching, 445-447 

in steel for the production of 
dies for coins, reliefs, etc., 
44 8, 449 
gilder's brush, 136 
gilding, first practical results in, 3 
magnet, 12 
magnetic induction machine, 

first, construction of, 4 
magnetism, 21-23 
magnets, 23 
metallurgy, historical review of, 

1-9 
motive force, 16 

of elements, table of, 

527 
or power, 33, 34 
or tension, coupling 
the elements 
for, 20 
series of, 15 
plated objects, finished, treat- 
ment of, 159-161 
plates, finishing the, 443, 444 
plating, additional rules for, 209, 
210 
arrangements in particular, 

97-131 
bath, requisites of a, 184 
chemical products and var- 
ious apparatus and instru- 
ments used in, 493-522 
establishment, ground plan 

of an, 125-129 
establishments in general, 

arrangement of, 93-131 
industry, lacquers used in 
the, 484, 485 



546 



INDEX. 



Electro-plating, mechanical treat- 
ment during and after, 156- 
161 
plant, parts of, 97 
tanks, Bossard, 178-180 
small articles en masse, 

apparatus for, 213-217 
treatment of metallic articles 
before, 132-156 
Electrodes, 26 
Electrolysis, 25-33 

consumption of power in, 33 
determination of copper in copper 
baths by, 277, 
278 
gold in gold 
baths by, 372 
silver in silver 
baths by, 336, 
337 
zinc in brass 
baths by, 290, 
291 
Electrolyte, 26 

Electrolytic determination of copper 

in the acid copper bath, 426, 427 

dissociation, Svante Arrhenius' 

theory of, 27-29 
method of analysis, 253-255 
plating apparatus for mechanical 
electro-plating, 180 
Electropoion, 43 
Electroscope, 13 
Element, bichromate, 58 
cupron, 53, 54 
Daniell, 38, 39 
described by Knaffe and Keefer, 

55, 56 
Dun's potash, 54, 55 
galvanic, 16 
Grove, 40^ 
Leclanche, 51 
Meidinger, 39, 40 
Oppermann, 47-51 
plunge, 59, 60 
Smee, 37, 38 
Stoerer's, 59 

Umbreit and Matthes, 53, 54 
Elements, arrangement with, 97-115 
Bunsen, manipulation of, 45, 46 
constant, 38 

coupling of, for electro-motive 
force or ten- 
sion, 20 
quantity of cur- 
rent, 20 
galvanic, 35-60 
mixed coupling of, 20 



Elements, secondary, 87-92 

table of electro-motive force of,. 
527 
with their symbols, 
atomic weights and 
specific gravities, 523 
various, 54 
Elmore's process of producing copper 

tubes, 460 
Eisner's bronze bath, 292 

tinning bath, 389 
Emery, kinds of, 144 
Endless belt machine or belt strap- 
ping attachment, 153, 154 
English horse-power, 34 
Essential resistance, 18 
Etching, electro, 445-447 

in steel for the produc- 
tion of dies for coins, 
reliefs, etc., 448, 449 
ground, 446, 447 
Ether, definition of, 15 
Evaporating dishes or capsules, 517 r 

518 
External resistance, 18 
Extra currents, 25 
Eyes, silvering of, 325 

tinning solution for, 388 

FAHRENHEIT, Centigrade and 
Reaumur thermometers, com- 
parison of the scales of, and rules- 
for converting one scale into an- 
other, 538 
Farad, the, 34 
Faraday, discovery by, 65, 66 

of chemical action of 
the current by, 26 
electric induction 
by, 4 
electrolytic laws of, 30-32 
Faure, improvement of the accumu- 
lator by, 88 
Fein bichromate battery, 56, 57 

dvnamo, 73, 74 
Felt wheels, 143 
Ferric oxide, 155 
sulphide, 500 
Ferrous sulphate, 510 
Fibre brush, 146 
Fibres, 146, 147 
Field, magnetic, 12, 66 

magnets, 67 
Filters, 520, 521 
Fine wheel, 144 
Fire gilder's brush, 136 

-gilding and electro-deposition, 
combination of, 369-371 



INDEX. 



547 



Fire or mercury gilding, 367-369 

Flasks, glass, 517 

Flexible shafts for grinding, polishing 

and buffing, 154, 155 
Flowers, coating of, with copper, 461 
Foot-lathe for polishing, 149 

-power grinding and polishing 
lathe, 150 
Foote's pinnacle gravity battery, 46, 47 
Force or power, 33 
Forks, extra coating of silver on the 
convex surfaces of, 319 

silver deposit on, 311 

slinging wires for, 310 
French form of cell-apparatus, 416, 417 

horse-power, 34 
Fulminating gold, 503 
Fundamental or C. G. S. units, 33, 34 

GALVANI, discovery of contact 
electricity by, 1 
experiments of, 1, 2 
Galvanic chain, 16 
current, 16 
element, 16 
elements, 35-6* > 

thermopiles, magneto- and 
dynamo-electric machines, 
35-92 
Galvanometer, 103, 104 

indications by the, 106-108 
Galvanometers, 22 
Galvanoplastic art, progress of, 5 

baths at rest and when agitated, 
table of results with, 422 
current-strength for, 437 
copper baths, contrivances for the 

agitation of, 423, 424 
deposition by the battery and 
dynamo, 418-425 
in the cell-apparatus, 413-418 
with accumulators, 438, 439 
the battery, 419, 420 
dynamo, 420-425 
method for originals in high re- 
lief, 458 
operator, pencils and brushes 

used by the, 1 36 
process, invention of, 5 
reproduction of busts, vases, etc., 
449-455 
Galvanoplasty, 412-468 
definition of, 412 
in iron, 463-467 
nickel, 467 

silver and gold, 467, 468 
matting by, 166 
Galvanoscopes, 22 



Gas carbon, 41, 42 

anodes, 199, 200 
Gassiot's method of producing me- 

tallo-chromes, 399 
Gauduin's copper bath, 267 
Gauze, gilding of, 358-360 
Gelatine moulds, 458-460 
Generators, electric, classes of, 69 
Gerhold's solution for tinning, 387 
German form of cell-apparatus, 417 
silver articles, gilded, stripping 
of, 371 
cleansing of, 171 
deposit of, 248, 249 
for spoons, preparation of, 

for plating, 318 
nickeling of, 203 
pickling of, 163 
preparation of, for silver- 
plating, 308, 309 
sheet, treatment of, 148 
silver-plating of, 317 
Gilded articles, stripping of, 371 

to give a beautiful, rich 
appearance to, 357 
Gilder of watch-works, brush used by 

the, 136 
Gilder's wax, 356, 357 
Gilding, bad tones of, to improve, 
357, 358 
by contact, baths for, 360-363 

by immersion and by fric- 
tion, 360-365 
dipping, baths for, 363-365 
friction, 366, 367 
cold, baths for, 342-344 
coloring of, 356-358 
combination of fire-gilding and 

electro-deposition of, 369-371 
defective, to improve, 3C3 
fire or mercury, 367-369 
genuine, determination, of, 371, 

372 
green, 354 

hot, baths for, 344, 345 
matt, 354-356 

metallic wire and gauze, 358-360 
preparation of articles for, 351 
porcelain, glass, etc., 365, 366 
red, 353, 354 
rose-color, 354 
spurious, of silvered brass articles, 

478 
with the cork, 366, 367 
rag, 366, 367 
thumb, 366, 367 
without a battery, 350, 351 
Girders, zinc-plating of, 393-395 



54 8 



INDEX. 



Glass balloons and flasks, 517 
gilding of, 365, 366 
jars, 518 

metallization of, 463 
platinizing of, 380, 381 
Glauber's salt, 509 
Glue pots, 153 

Gold amalgam, preparation of, 367 
analyses of, 339 
and silver, galvanoplasty in, 467, 

468 
baths, 341-346 

current-density for, 350 

strength for, 351 
examination of, 372, 373 
management of, 346-353 
preparation of, with the as- 
sistance of the electric cur- 
rent. 345 
recovery ofgold from, 373, 374 
strengthening of, 372, 373 
vats for, 349, 350 
capsule for discoloring, 361 
chloride, 503 
color, pale, on brass, 475 
deposition of, 339-374 
deposits, polishing of, 160, 353 
in gold baths, determination of, 

by electrolysis, 372 
incrustations with, 329, 330 
painter's, 340 

-plating, execution of, 350-353 
in the cold bath, process of, 
352 
hot bath, process of, 
352, 353 
use of carbon anodes in, 348 
platinum anodes in, 348 
steel anodes in, 346-348 
properties of, 339, 340 
scratch-brushing of, 157 
shell, 340 
solder, 531 

varnishers, operations of, 485, 486 
Gore, bath for brassing cast-iron, 
wrought-iron and steel, recom- 
mended by, 284, 285 
Gountier's solution for coating 
wrought- aud cast-iron with bronze, 
292 
Goze's process for obtaining a deposit 
. of aluminium, 408 
Graining, 326-329 

preparations for, 327 
Gramme armature, 70 
dynamo, 8, 70, 71 
Grasses, coating of, with copper, 461 
Gravimetric analysis, 251, 252 



Gray color with a bluish tinge on 
brass, 475 
yellow, brown to black colors on 
zinc, 480 
Gray's researches, 13 
Grease, removal of, from metallic 

articles, 169-171 
Green gilding, 354 

vitriol, 510 
Grinding, 142-144 

and polishing foot power lathe, 
150 
lathes electrically 
driven, 152 
execution of, 146 
flexible shafts for, 154, 155 
lathes, 145-147 

transmission for, 97 
rooms used for, 96, 97 
wheels, treatment of, 144, 145 
wooden, 142, 143 
Grove element, 40 

Giilcher's thermo-electric pile, 63-65 
Gun barrels, browning of, 481, 482 

metal, 280 
Gutta-percha, introduction of, 5 
moulding in, 428-431 
oil, 451 
softening of, 428-431 

HAEN'S method for the volumet- 
ric determination of copper in 
the acid copper bath, 425, 426 
Hansen & Van Winkle Co. 's dynamo, 

82-85 
lathe manufact- 
ured by, 150- 
152 
plating -room 
arranged by, 
129 
voltmeter, 121 
Hard nickeling, baths for, 242, 243 

solder, 530 
Hassauer's copper bath, 262 
Hauck's thermo-electric pile, 62, 63 
Heads, moulding of, 450, 451 
Hefner-Altenbeck's drum armature, 
74 
machine, 8 
Heliography, 447, 448 
Helix, 12 

Herz, Prof., investigations of, 15 
Historical review of electro-metal- 
lurgy, 1-9 
Hittorf 's experiments, 29 
Hoe & Co.'s electric connection 
gripper, 435 



INDEX. 



549 



Hollow ware, gilding of, 352 

preparation of, for plating, 
318 
Hooks, silvering of, 325 

tinning solution for, 388 
Horizontal galvanometer, 103 
Horse-power, English, 34 

French, 34 
Hot gilding, baths for, 344, 345 
Hiibl, experiments of, 412, 413 
Hydraulic moulding press, 430, 431 
Hydrochlorate of zinc, 501 
Hydrochloric acid, 494 
Hydrocyanate of silver, 506 

zinc, 506 
Hydrocyanic acid, 494, 495 

poisoning by, 490, 
491 
Hydro-electric current, 16 
Hydrofluoric acid, 496, 497 
Hydrogen sulphide apparatus, con- 
struction of a, 67-69 
Hydrometer, estimation of the condi- 
tion of baths by the, 175, 176 
Hydrometers, 518-520 
Hydroplatinic chloride, 503, 504 
Hj'drosulphate of ammonia, 499 
Hydrosulphuric acid, 498 
Hygienic rules for the work shop, 

489-492 
Hyponitric gas, poisoning by, 492 

TDIO -ELECTRICS, 13 

X Incrustations with silver, gold 

and other metals, 329, 330 
Induced current, 24 
Induction, 23-25 

electric, discovery of, 4 
Inductive current, 24 
Inlaying of coppered art-castings, 274 
Instruments and apparatus, various, 

517-522 
Internal resistance, 18 
Ions, division of, 27, 28 
Iridescent colors, 397-399 
Iridium, deposition of, 382 
Iron-ammonium sulphate, 510 

articles, badly rusted, to cleanse, 
162 
copper baths for, 262 
coppering of, 273 
grinding of, 147, 148 
pickling of, 162 
silvered, stripping of, 333 
tinning solution for, 388 
baths, 400-402 

management of, 402, 403 
black color on, 482, 483 



Iron, blue color on, 483 

brassed, brown black color on, 

476 
brassing of, 283 
brown-black coating with bronze 

lustre on, 483, 484 
cast, brassing bath for, 284, 285 
solution for coating with 

bronze, 292 
tin-bath for, 384 
zincking bath for, 392 
castings, unground brassing of, 

289 
clock cases, dead black coating 

on, 483 
coloring of, 481-484 
current-density for nickeling, 206 
deep black deposit of, 401, 402 
deposition of, 399-403 
deposits, analysis of, by Leuz, 464 
electro-deposition of, principal 

use of, 399 
electrolytically deposited, 466 
excellent pickle for, 162 
galvano plasty in, 463-467 
heavy and very hard deposit of, 

bath for, 400 
lustrous black color on, 482 
nickel bath for, 195 
nickeling of, 203, 204 
objects, cleansing of, 171 
sheet, coppering of, 271 

nickeling of, 237, 238 
silvering of, early knowledge of, 1 
silver-plating of, 816 
to give to, a silvery appearance 

with high lustre, 484 
wire and plates, table of weight 

of, 536 
wrought, brassing bath for, 284, 
285 
solution for coating with 

bronze, 292 
zincking bath for, 392 

of, by contact, 395 
zinc-plating objects of, 393- 
395 

JACOBY, Prof, invention of the 
galvano-plastic process by, 5 
Jars, glass, 518 
Jordan, C. J., claim of, to the inven- 
tion of the galvano-plastic process, 5 
Joule's experiments, 32 

KAISER, deposition of an alloy 
containing nickel according to, 
247 



550 



INDEX, 



Kations, 26, 28 

Keiser and Schmidt's bichromate 

battery, 57 
Kettles, 181 

Klein's bath for galvano-plasty in 
iron, 464 
method for the production of 
copper tubes, 460, 461 
Knaffe and Kiefer, element described 

by, 55, 56 
Knife blades, nickeling of, 240, 241 
Knight's process of black-leading, 

433, 434 
Knives, silver deposit on, 310, 311 
Kofner's sheet polishing machine, 

228-230 
Kristaline, 487, 488 
Krottlinger dynamo, 76, 77 
Krupp-Gousonwerk sheet polishing 

machine, 230-232 

LACES, coating of, with copper, 460 
Lacquering, 484-488 
Lacquers and varnishes, cellulose, 
487, 488 
application of, 485 
Lahmeyer dynamo, 77-89 
Lallande and Chaperon element, 51-53 
Lamp feet, cast zinc, nickeling of, 209 
Langbein & Co., apparatus for electro- 
plating small articles, 

214 
dynamo, 79, 89 
plunge element, 59, 
60 
La Pierre patent sand blast, 137 
Lathe-brush for scratch-brushing, 159 
foot-power for polishing, 149 

grinding and polishing 
150 
, manufactured by the Hanson & 
Van Winkle Co., 150-152 
Lathes, double polishing, 150 
grinding, 145-147 

and polishing, electrically 
driven, 152 
ansmissioi 
Law, Coulomb's, 15 

Ohm's, 17, 18 
Lead acetate, 517 
baths, 397 
cleansing of, 171 
deposition of, 396-399 
nickeling of, 203 
salts, poisoning by, 491 
Leading by contact, 397 
Leather, plates for the production of 
imitations of, 462 



Leaves, coating of, with copper, 461 
metallization of, 455-457 

Leclanche element, 51 

Lenoir's galvanoplastic method for 
originals in high relief, 458 

Lenz's analysis of iron deposits, 464 

Liebenow and Loeb's theory of the 
accumulator, 90, 91 

Lignite, 210 

Lime, burnt or quick, 498 

mixture or paste, preparation of, 

170 
Vienna, 498 

Line, neutral, 11 

Lines of force, 66 

" Little Wonder " dynamo, 81 

Liver of sulphur, 498, 499 

Loadstone, 10 

London Metallurgical Co., areas sil- 
ver-plating, patented by, 306-308 

Lunar caustic, 514, 515 

MACHINE, to find the speed of a, 
537, 538 
Magnet, artificial, 10 
Magnetic field, 12, 66 
iron ore, 10 
machine, 7 
meridian, 11 
needle, determination of the 

direction of the, 21 
poles, 10, 11 
Magnetism, 10-12 

Ampere's theory of, 11, 12 
and electricity, 10-34 
Magneto- and dynamo-electric ma- 
chines, 65-87 
-electric machine, transition of 
the, to the dynamo, 68 
Magnets, field, 67 

Mannesmann Pipe Works, process of 
the, for deposits upon alumin- 
ium, 411 
Marble, 508 

Matrices in plastic material, prepara- 
tion of, 427, 428 
Matt-black on copper, 471, 472 
-gilding, 354-356 
-grained surface, production of a, 
165 
Matting, 164-166 

by chemical means, 165 
galvanoplasty, 166 
mechanical means, 165, 166 
Mechanical electroplating, electro- 
lytic plating apparatus for, 180 
treatment during and after elec- 
tro-plattng, 156-161 



INDEX. 



551 



Mechanical treatment of metallic ar- 
ticles, 132-161 
Mechano electro-plating tanks, Boss- 

ard, 178-180 
Medium wheel, 14-4 
Meidinger element, 39, 40 
Mercuric nitrate, 514 
Mercurous nitrate, 514 
Mercury or fire-gilding, 367-369 

salts, poisoning by, 491 
Meriden Britannia Co's practice of 
silver-plat- 
ing, 317,318 
sil ver- plating 
solution, 318 
striking solu- 
tion, 318 
Meridian, magnetic, 11 
Meritens's process of coloring iron 

black, 482, 483 
Metal, regaining of, from exhausted 

dipping baths, 168, 169 
Metallic alloys for moulds, 452 

articles, chemical treatment of, 
161-172 
mechanical treatment of, 132- 

161 
removal of grease from and 

cleansing, 169-171 
treatment of, 132-172 

before electro- 
plating, 132- 
156 
chromes, 397-399 
powders, metallization by,457, 458 
surface, making a copy from a, 
444, 445 
Metallization by metallic powders, 
457, 458 
the wet way, 455-457 
Metals, coloring, patinizing, oxidiz- 
ing, etc., of, 469-488 
conducting power of, 17 
incrustations with, 329, 330 
reduction of, without a battery, 

184, 185 
table of melting points of, 531 
Milk pitchers, gilding of, 352 
Mineral kermes, 479 
Molecules, Clausius' theory of, 26, 27 
Monopotassic carbonate, 507 
Montgomery, Dr., introduction of 

gutta-percha by, 5 
Motors, directly connected, to ma- 
chines, 85, 86 
Mould, detaching the shell from the, 

439 
Moulding busts, 450, 451 



Moulding compositions, 431 
heads, 450, 451 
in gutta-percha, 428-431 

wax, 431 
press, 429, 430 

hydraulic, 430, 431 
surfaces in relief, 450 
with metallic alloys, 452 

oil gutta-percha, 451, 452 
Moulds, black-leading of, 431-434 
gelatine, 458-460 
in plastic material, preparation 

of, 427, 428 
suspension of, in the bath, 435, 
436 
Multipliers, 22 
Muriate of gold, 503 
zinc, 501 
Muriatic acid, 494 

Murray, discovery by, of making non- 
metallic surfaces conductive, 5 

NAIDS, zincking of, 395 
Nature-printing, 460 
Needles, tinning of, 389 
Nees's process for electro-depositions 

upon aluminium, 411 
Negative electricity, 18 

wire, 109 
Neutral line, 11 

zone, 11 
Nicholson and Carlisle, decomposi- 
tion of water by electrolysis by, 3 
Nickel alloys, deposits of, 247-249 
ammonium sulphate, 512 
and cobalt, deposition of, 186-260 
anodes, 198-202 

reddish tinge of, 202 
bath, arrangement of anodes for 
a, 208, 209 
coupling of Bunsen elements 

for a, 98 
for production of thick de- 
posits, 196, 197 
small articles, 196 
most simple, 190 
without nickel salt, 198 
baths, 187-198 

addition of bisulphide of car- 
bon to, 196 
containing boric acid, 192- 

194 
determination of acidity and 
alkalinity 
of, 189, 190 
acids in, 249, 
250 
electrolytic analysis of, 255 



552 



INDEX. 



Nickel baths, examination of, 249-256 
first requisite in preparing, 

187 
for special purposes, 194-196 
freshly-prepared, working of, 

197 
heating of, 198 
old, recovery of nickel from, 

244 
refreshing of, 220, 221 
restoring the neutrality of, 

202 
wooden vats lined with lead 
for, 110, 111 
bronze, 247, 248 
carbonate, 509 
chloride, 502 
copper and zinc, deposition of an 

alloy of, 248 
deposition of, 186-256 

from its double 
salt, 6 
deposits, polishing of, 160, 221 
electrotypes, 467 
galvanoplasty in, 467 
patent for the deposition of, 6 
-plating, additional rules for, 209, 
210 
criteria for the correct pro- 
gress of, 206 
current-strength for, 205, 206 
principal phenomena, which 
mav occur in, and their 
avoidance, 218-220 
process of, 202-211 
solid, 207 

test for sufficiently solid, 208 
treatment of articles after, 

221 
yellowish tone of, remed} 7 
for, 218 
properties of, 186, 187 
salts, solution of, 181, 182 
scratch-brushing of, 157 
silver for spoons, preparation of, 
for plating, 318 
-plating of, 317 
solutions, eruptions caused by, 

490 
sulphate, 511, 512 
various colors upon, 473, 474 
Nickeled articles, removal of moist- 
ure from, 159, 160 
stripping of, 217, 218 
Nickeling, 186-256 

by contact and boiling, 245-247 
defective, to improve, 244, 245 
electrotypes, 242-244 



Nickeling en masse of small and! 
cheap objects, 211-217 
hard, baths for, 242, 243 
knife blades, sharp surgical in- 
struments, etc., 240, 241 
of a dark tone, bath for, 195 
printing plates, 242-244 
salts, prepared, 187 
sheet iron and sheet steel, 237,. 
238 
zinc, 221-236 
skates, 241, 242 
tin-plate, 236 
wire, 238-240 
gauze, 240 
Niel, imitation of, 330, 331 
Niello, Corvin's, 461 
Nitrates, 513-515 
Nitre, 513, 514 
Nitric acid, 494 

table of specific gravity and' 
content of, 533 
Nitrous gas, poisoning by, 492 
Nobili, production of iridescent 

colors by, 4 
Nobili's rings, 397-399 
Noe's thermo-electric pile, 61 
Non-electrics, 13 

■essential resistance, 18 
Norris and Johnson's brass bath, 284,. 

285 
North pole, 11 



OBERNETTER'S method of steel- 
ing copper printing plates, 400, 
401 
Object-wire, 109 

main, and main anode wire, 
coupling of the, with the 
resistance boards, volt- 
meter, switch and baths, 
123. 124 
Oersted, Prof., discoveries of, 3, 4 
Ohm, the, 34 
Ohm's law, 4, 17, 18 

proposition deduced from,. 
20, 21 
Oil gutta-percha, 451 
Oil of vitriol, 493, 494 
Opperman element, 47-51 
Organic acids, salts of, 516, 517 
Orpimeut, 499, 500 
Osmotic pressure, 29 
Oxalate platinum bath, 378 
Oxidized silver. 332 
Oxidizing, patinizing, coloring, etc., 
of metals, 469-488 



INDEX. 



553 



PACINOTTI, invention by, of the 
ring named after him, 8 
ring armature of, 68 
Painter's gold, 340 
Palladium baths, 382 

deposition of, 381, 382 
properties of, 381 , 382 
Paracelsus, silvering of iron and cop- 
per known to, 1 
Paris Mint, method in the, for pro- 
ducing brown color upon cop- 
per, 470 
Parkes's method of metallization, 455- 

457 
Pasteboard wheels, 143 
Pastes, argentiferous, for cold silver- 
ing, 326 
Patent Uuderwriter's switch board or 

rheostat, 104, 105 
Patina, definition of, 460 

genuine, imitation of, 472, 473 
Patinizing, oxidizing, coloring, etc. 

of metals, 469-488 
Pfanhauser's brassing bath, 285, 286 
copper bath, 267 
plating drum, 214, 215 
_ tin bath, 385 
Philipp's process of coating laces and 

tissues with copper, 460 
Phosphate platinum bath, 378, 379 
Phosphates and pyrophosphates, 515 
Pickle for iron, 162 

preliminary, 163 
Pickling, 115 

absorbing plant for the vapors 

evolved in, 167, 168 
and dipping, 162-164 
duration of, 162, 163 
in the electrolytic way, 162 
main points in, 166, 167 
production of a matt-grained sur- 
face by, 165 
Pile of Volta, 2, 35 
Piles, thermo electric, 60-65 
Pillet's palladium bath for watch- 
movements, 382 
Pins, nickeling of, 211 
silvering of, 325 
tinning solution for, 388 
Pitchers, gilding of, 352 
Pixii, construction of the first electro- 
magnetic-induction machine 
by, 4 
electrical machine constructed 
by, 68 
Plante accumulators, 87, 88 
Plaster of Paris, making of, impervi- 
ous to fluids, 454, 455 



Plaster of Paris, moulding in, 452-454 
Plater's lathe goblet scratch-brush, 

134 
Plating balance, 312-314 
drum, 214, 215 

room arranged by the Hanson & 
Van Winkle Co., 129 
floor of, 95 
heating of, 94, 95 
light and ventilation in, 93, 

94 
size of, 96 
water for, 95 
Platinic chloride, 503, 504 
Platinizing by contact, 381 

glass, 380, 381 
Platinum anodes, 199 

insoluble, 299, 300 
use of, in gold-plating, 
348 
baths, 375-379 

management of, 379, 380 
deposition of, 375-381 
deposits, polishing of, 160 
-plating, execution of, 380 
properties of, 375 
recovery of, from platinum solu- 
tions, 381 
Platoso-ammonium chloride, prepa- 
ration of, 375 
Plunge batteries, 56 
element, 59, 60 
Poisoning by alkalies, 491 
arsenic, 491 
copper salts, 491 
chlorine, sulphurous 
acid, nitrous and hy- 
ponitric gases, 492 
hydrocyanic acid, po- 
tassium cyanide or 
cyanides, 4C0, 491 
lead salts, 491 
mercury salts, 491 
sulphuretted hydrogen, 
491,492 
Polarizing current, 27, 210, 211 
formation of, 30 
phenomena, 210, 211 
prevention of, 37 
Pole, north, 11 
pieces, 67 
south, 11 
Poles, attraction and repulsion of, 11 
Polishing, 148-156 

copper deposits, 270,271 
dust in, prevention of, 97 
flexible shafts for, 154, 155 
gold deposits, 353 



554 



INDEX. 



Polishing lathes, double, 150 
materials, 155, 156 
nickel deposits, 221 
rooms used for, 96, 97 
wheels or bobs, 148, 149 
Poole, M., first use of thermo-elec- 
tricity by, 6 
Porcelain, deposit of copper upon, 463 
gilding of, 365, 366 
metallization of, 463 
Positive electricity, 13 

wire, 109 
Potash, 507 

alum, 509, 510 
bicarbonate of, 507 
caustic, 497 
element, Dun's, 54, 55 
yellow, prussiate of, 506, 507 
Potassium and sodium amalgam, pro- 
duction of, 4 
bitartrate, 516 
carbonate, 507 

in silver baths, determination 

of, 335 
solutions, table of specific 
gravity and content of, 531 
cyanide, 174, 504, 505 
handling of, 490 
free, in brass baths, deter- 
mination of, 290 
in silver baths, deter- 
mination of, 334 
in copper baths, determina- 
tion of, 275-277 
poisoning by, 490, 491 
solutions, introduction of, 5, 6 
use of as a pickle, 164 
with a different content, table 
of, 505 
discovery of, 3 
ferro-cyanide, 506, 507 
hydrate, 497 
nitrate, 513, 514 
-sodium tartrate, 516 
sulphide, 498, 499 
Potential, 16, 33, 34 
Pottery, deposit of copper upon, 463 
Power, consumption of, in electro- 
lysis, 33 
or force, 33 
Press, moulding, 429, 430 
Pressure, osmotic, 29 
Primary current, 24 
Printing plates, copper, galvanoplas- 
tic bath for, 421 
steeling of, 400, 
401 , 403 
Protosulphate of iron, 510 



Prussiate of potash, white, 504, 505 
silver, 506 
zinc, 506 

Prussic acid, 494, 495 

poisoning by, 490, 491 

Pulley on counter-shaft carrying belt 
to machine, to find diam- 
eter of, 537 
main shaft, to find diameter 
of, 537 

Pyrophosphates and phosphates, 515 

QUADRIVALENT kations, 28 
Quantity, 33 
of current, 17-21 
Quick lime, 498 
Quicking, 309 

RAIN water, 173 
Ratsbane, 496 
Rauber's sheet grinding and polish- 
ing machine, 224-228 
Reaumur, Centigrade and Fahrenheit 
thermometers, comparison of the 
scales of, and rules for converting 
one scale into another, 538 
Recovery of gold from gold baths, 
373, 374 
nickel from old baths, 

244 
platinum from plati- 
num solutions, 381 
Red brass, 280 

brown-color on copper, 471 

dark, on brass, 477 
shades on zinc, 481 
gilding, 353, 354 
sulphide of antimony, 499 
Region of the lines of force, 66 
Reinhold's aluminium bath, 408 
Relief, surfaces in, moulding of, 450 
Reliefs, dies for, production of, 448,449 
Resinous electricity, 13 
Resist, composition of, 328 
Resistance, 16, 17, 34 
-board, 101-10S 
total, composition of, 18 
Rheostat, 101-103 

patent underwriters, 104, 105 
Rhodium, deposition of, 382 
Rieder's process of electro-etching in 
steel for the production of dies for 
coins, reliefs, etc , 448, 449 
Ring armature, Paciuotti's, 68 
River water, 173 
Rivets, nickeling of, 211 
Rochelle salts, 516 
Rock salt, 500 



INDEX. 



555 



Rods, plating apparatus for, 216 

Rogers Manufacturing Co., amount of 
silver depos- 
ited upon 
plated table 
ware, manu- 
factured by, 
311 
preparation of 
work for 
plating by, 
318 
silver-plating 
solution 
used by, 318 
striking solu- 
tion used 
by, 318 

Rose-color gilding, 354 

Roseleur's plating balance, 312-314 
solutions for tinning, 387 

Rouge, 155 

Roughing wheel, 144 

Ruolz's bronze bath, 292 

SAL AMMONIAC, 500 
solutions, table of specific 
gravity of, 533 
Salt, common, 500 

rock, 500 
Saltpetre, 513, 514 
Salts of organic acids, 516, 517 
Salzede's bronze bath, 292 
Sand-blast, matting with the, 166 

-blasts, 136-139 
Sawdust, 159 

Saxton and Clarke, invention by, 68 
Schaag's process of zincking, 391 
Schlippe's salt, preparation of, 405 
Schuckert dynamo, 8, 72, 73 
Schultz's patent for prevention of 

stains in copper-plating, 270 
Scratch-brushes, circular, 134, 135 
forms of, 133, 134 
-brushing, 133-136, 156-159 
lathe-brush for, 159 
liquids used in, 157 
Screws, zincking of, 395 
Secondary current, 24 

element, 87-92 
Seebeck, Prof., discovery of, 60 
Seignette salt. 516 

Shafts, flexible, for grinding, polish- 
ing and buffing, 154, 155 
Shaving machines for electro-plates, 

443 
Sheet iron, coppering of, 271 

nickeling of, 237, 238 



Sheet polishing machines, 224-232 
steel, nickeling of, 237, 238 
zinc, coppering of, 271 
nickeling of. 221-236 
Shell, backing the, 440-442 

gold, 340 
Siemens, Dr. W., discovery by, 68, 69 
improvement by, 68 
& Halske dynamo, 8, 74-76 
Silver, amount of, deposited upon 
table ware, 311 
and gold, galvanoplasty in, 467, 

468 
anodes, 298 

articles, gilded, stripping of, 371 
baths. 295-298 

addition of potassium cyanide 
to, 300 
silver to, 301 
agitation of, 303, 304 
augmenting the content of 

silver in, 302 
" bright-plating," prepara- 
tions for, 304, 305 
coupling of elements for, 98 
determination of the proper 
proportions of silver and 
potassium cyanide in, 302 
examination of, 334-337 
free potassium cyanide in, 

determination of, 334 
gradual thickening of, 301, 

302 
improvement of, by organic 

substances, 305, 306 
insoluble platinum anodes 

for, 299, 300 
most suitable current- 
strength for, 299 
old, recovery of silver from, 

337-339 
potassium carbonate in, de- 
termination of, 335 
prepared with chloride of sil- 
ver, life of, 301 
silver in, determination of, 

336,337 _ 
strengthening of, 337 
treatment of, 298-308 
chloride, 502, 503 

preparation of silver bath 
with, 296, 297 
control of the weight of the de- 
posit of, 311-314 
cyanide, 506 

preparation of silver bath 
with, 297 
deposition of, 294-339 



556 



INDEX. 



Silver deposits, polishing of, 160 

heavy deposits of, baths for, 295- 

297 
in silver baths, determination of, 

336, 337 
incrustations with, 329, 330 
-nickel alloy, deposit of, 306 
nitrate, 514, 515 
oxidized, 332 

-plated articles, yellow tone of,306 
-plating, areas, 306-308 
balance, 312-314 
by weight, 308-315 

baths for, 295-297 
determination of, 333, 334 
execution of, 308-320 
Meriden Britannia Co. 's prac- 
tice of, 317, 318 
ordinary, 315-320 

bath for, 298 
statistics of quantity of silver 
used in, 295 
powder for graining, preparation 

of, 327 
properties of, 294 
recovery of, from old silver baths, 

337-339 
scratch-brushing of, 157 
solder, 530 

striking solutions, 318 
Silvered articles, stripping of, 333 
yellow color on, 332 
Silvering, antique, 331, 332 

articles of copper-alloys, 323-325 
by contact, by immersion and 
cold silvering with paste, 
320-326 
immersion, baths for, 320, 321 
cold, with paste, 325, 326 
current-density for, 100 
fine copper wire, 329 
nielled, imitation of, 330, 331 
old, 331, 332 
Similor, 280 
Sine galvanometer, 22 
Single fluid hypothesis of electricity, 

14,15 
Siphons, 521, 522 
Skates, nickeling of, 241, 242 
Slinging wires, 114 

for forks and spoons, 310 
Smee, discoveries of, 6 
element, 37, 38 
experiments by, 412 
Smith & Deakin, apparatus of, for 

electro-plating small articles, 313 
Smoke-bronze, 477 
Soda, caustic, 497 



Soda, washing. 507, 508 
Sodium and potassium amalgam, pro- 
duction of, 4 
bicarbonate, 508 
bisulphite, 513 
carbonate, 507, 508 
chloride, 500 
citrate, 517 
discovery of, 3 
hydrate, 497 
nitrate, 514 
phosphate, 515 
pyrophosphate, 515 
sulphate, 509 

varieties of, 174 
sulphide solution, preparation of, 

321-323 
sulphite, 513 
Soft solder, 530 
; Soldering fluid, 440, 441 
j Solders, table of, 530, 531 
j Solenoid, 12, 23 
■ Solubility of various substances, table 

of, 528 
Sources of current, 35-92 
South pole, 11 
Sparking, causes of, 116 
Specific gravity, estimation of the 

condition of baths by the, 175, 176 
Speed, rules for, 537, 538 
Spencer, T. , claim of, to the invention 
of the galvanoplastic 
process, 5 
electro-etching, invented 
by. 445 
Spirit of nitre, 494 
Spirits of hartshorn, 497, 498 
Spoons, extra coating of silver on the 
convex surfaces of, 319 
slinging wires for, 310 
silver deposit on, 311 
Spring water, 173 
Stannic chloride, 501 
Stannous chloride, 501 
Starrett improved volt-meter, 120 
Stearine, moulding in, 431 
Steel anodes, use of, in gold-plating, 
346-348 
articles, cleansing of, 171 
cobalt bath for, 258, 259 
copper bath for, 262 
coppering of, 273 
grinding of, 147, 148 
tinning solution for, 388 
bath for brassing, 284, 285 

forzincking, 392 
baths, 400-402 
blue color on, 483 



INDEX, 



557 



T 



Steel clock cases, dead black coating i Switch 
on, 4^3 
current-density for nickeling, 206 J 
cutlery, preparation of, for plat- 
ing, 318 
electro-etching in, for the produc- 
tion of dies for coins, reliefs, 
etc., 448, 449 
galvanoplasty in, 403-167 
gray color upon brass, 475 
copper, 473 
nickeling of, 203, 204 
pens, coppering of, 273, 274 
sheet, nickeling of, 237, 238 
silver-plating of. 31b, 317, 318 
spring carboy rocker, 172 
Steeling, 399-403 

by contact, 403 
Stoerer's element, 59 
Stolbe's method of tinning, 390 

nickeling process by contact, 
245, 246 
Stone-ware, deposit of copper upon, 
463 
vats, 112 
Stopping off, 319. 320 
Straw color to brown, through gold- 
en yellow, and tombac color on 
brass, 475 
Striking solutions, 318 
Stripping acid, 217 

gold from gilded article, 371, 372 
nickeled articles, 217, 218 
silvered articles, 333 
Sugar of lead, 517 
Sulphate of iron, 510 
Sulphates and sulphites, 509-513 
Sulphur combinations, 498-500 
Sulphuretted hydrogen, 498 

poisoning by, 491, 492 
Sulphuric acid, 403, 494 

free, determination of, 250 
solutions, different, table 
of specific electrical 
resistances of, at vari- 
ous temperatures, 526 
table of specific gravity 
of, 532 
Sulphurous acid, poisoning by, 492 
Sulphydrate of ammonia, 499 
Sulphydric acid, 498 
Surgical instruments, coating the 
wooden handles of, I 
with copper, 462, 463 i 
sharp, nickeling of, 
240, 241 
Svante Arrhinius's theory of electro- 
lytic dissociation, 27-29 
Swing brush, 133, 134 ' 



board, 101-103 

Patent Underwriters', 104, 
105 



ABLE for freeing articles 
grease, 127, 128 



from 



of actual diameters in deci- 
mal pans of an inch 
corresponding to the 
numbers of the vari- 
ous wire gauges, 535 
approximate content of 
blue vitriol in solutions 
at different degrees Be, 
417,418 
chemical and electro- 
chemical equivalents, 
524, 525 
composition of alloys 

and solders, 528-531 

electrical resistance of 

pure copper wire of 

various diameters, 534 

electro-motive force of 

elements, 527 
elements, with their sym- 
bols, atomic weights 
and specific gravities, 
523 
high temperatures. 531 
melting points of some 

metals, 531 
potassium cyanide with a 

different content, 505 
readings of different hy- 
drometers, 519 
resistance and conduc- 
tivity of pure copper at 
different temperatures, 
534 
results with galvano- 
plastic baths at rest, 
and when agitated, 422 
solubility of various sub- 
stances, 528 
specific electrical resis- 
tances of different 
sulphuric acid so- 
lutions at various 
temperatures, 526 
gravity and content 
of nitric acid, 
533 
of and content of 
solutions of 
potassium car- 
bonate, 531 
of sal ammoniac 
solutions, 533 



558 



INDEX. 



Table of specific gravity of sulphuric 
acid, 532 
resistance of differ- 
ent copper sul- 
phate solutions at 
various tempera- 
tures, 526 
value of equal current 
volumes as expressed 
in amperes per square 
decimeter, per square 
foot, and per square 
inch of electrode sur- 
surface, 525, 526 
weight of iron, copper 
and brass wire and 
plates, 536 
Tables, useful, 523-538 
Table-ware, plated, amount of silver 

deposited upon, 31 1 
Tangent galvanometer, 22 
Tanks, Bossard mechano-electroplat- 
ing, 178-180 
or vats, 109-112 
Tartar emetic, 516 

Taucher's bath for gilding by contact, 
360-363 
tin bath, 385, 386 
Temperatures, high, table of, 531 
Terchloride of gold, 503 
Terra-cotta. metallization of, 463 
Thermo-electric poles, 6(1— Go 
electricity, first use of, 6 
Thermometers, c> ating mercury ves- 
sels of, with copper, 463 
Fahrenheit, Centigrade and Reau- 
mur, comparison of the scales 
of and rules for converting one 
scale into another, -S38 
Thompson, Prof. S. P , definition of 

a dynamo electric machine by, 67 
Tin articles, silver-plating of, 316 
baths, 383-386 

current for, 386 
management of, 386, 387 
refreshing of, 386 
chloride, 501 
coloring of, 484 
deposition of, 383-390 
deposits polishing of, 160 
durable coating of, 389 
-plate, nickeling of, 236 
-plating, process of, 387 
properties of, 383 
salt, 501 

choice of, 386 
zinc, lead and iron, deposition of, 
383-403 



Tinning bv contact and boiling, solu- 
tions for, 387-390 
Tissues, coating of with copper, 460 
Toggle press, 429, 430 
Tombac, 280 

articles, silvered, spurious gild- 
ing of, 478 
cleansing of, 171 
deposits of, 293 
nickeling of, 203 
pickling of, 163 
Tripoli, 155 
Trivalent anions, 28 

kations, 28 
Trough battery, Cruikshank's, 2, 3, 

35 
Tumbling barrel, adjustable oblique, 
141, 142 
or drum, 139-141 
Twaddle hydrometer, 519 

UMBEREIT and Matthes element, 
53, 54 
Union canvass wheel, 149 
United States, evolution of the dyna- 
mo for plating purposes in the, 
80-82 
Units, electric, 33, 34 
Univalent anions, 28 
kations, 28 

\f ARNISH, stopping off, 319, 320 
Varnishes and lacquers, cellulose, 
487, 488 
composition of, 486, 487 
for gold varnishers, 486 
Varrentrapp's iron bath, 4« 
Vases, galvanoplastic reproduction 

of, 449 455 
Vats and tanks, It 9-112 
for heating baths, 112 
or tanks, 109-112 
wooden, 109, 110 

lined with lead, for copper 
and nickel baths, 110, 111 
Verdigris, 516, 517 
Vertical galvanometer, 103, 104 
Vienna lime, 145, 155, 498 
Villon's process for electro-deposi- 
tions upon aluminium, 410, 411 
Violet color on brass, 477, 478 
Vitreous electricity, 13 
Vitriol, blue. 510,511 
green, 510 
white, 511 
Volt, the, 34 
Volta, A., 1, 2 
Voltaic pile, 2, 35 



INDEX. 



559 



Voltmeter. Hanson & Van Winkle, 121 

Starrett improved, 120 
Voltmeters, 118-123 
Volumetric analysis, 252, 253 

determination of copper in acid 
copper 
bath, 425, 
426 
in copper 
baths, 278- 
280 
zinc in brass 
baths, 291 

WAHL, DR. W. H., directions for 
preparing platinum baths by, 
375-379 
Walenn's copper bath, 266, 267 
Walrine wheel, 149 
Walrus-hide wheels, 147, 148 
Warren's cobalt solution, 258 
Washing soda, 507, 508 
Watch movements, plating of, with 

palladium, 382 
Watches, graining parts of, 326, 327 
Water, 173 

decomposition of, by electro- 
lysis, 3 
power of dissociation of, 28 
Watt, the, 34 
Wax, gilder's, 356, 357 

moulding in, 431 
Weil and Newton's bronze bath, 292 
Weil's copper bath. 266 

method of zincking, 396 
Weiler, L. , conducting power of met- 
als according to, 17 
Well water, 173 
Weston ammeter, 121, 122 

boric acid as an addition to baths 

recommended by, 188, 189 
dynamo, 81 
nickel bath, 192 
voltmeter, 121 
Wheatstone, Sir C, discovery by, 68, 

69 
Wheel. Union canvass, 149 

walrine, 149 
Wheels, grinding, 142-144 

treatment of, 144, 145 
polishing, 148, 149 
walrus-hide, 147, 148 
White arsenic, 496 

metal, silver-plating of, 317 
prussiate of potash. 504, 505 
vitriol, 511 
Whiting, 508 
Wilde machine, 8 



Wire, anode, 109 

-carriers, special, 117 
copper, silvering of, 329 
current-carrying, size of, 108 
-gauges, table of actual diameters 
in decimal parts of an inch cor- 
responding to the numbers of 
the various, 535 
gauze, nickeling of, 240 
gilding of, 358-360 
negative, 109 
nickeling of, 238-240 
positive, 109 
Wires, conducting, calculating the 
thickness of, for dyna- 
mos, 129, 131 
insulation of, 109 
slinging, for forks and spoons, 310 
Wollaston, discovery by, 3 
Wood, coating of, with copper, 462 
Wooden grinding wheels, 142, 143 

vats, 109. 110 
Woolrj^ch. first magnetic machine, 

constructed by. 7 
Work, 33 
Workshop, hygienic rules for the, 

489-492 
Wright, introduction by, of the use of 

potassium cyanide solutions, 5, 6 
Wrought iron articles, pickling of. 162 
zinc-plating of, 393- 
395 
bath for brassing, 284, 
285 
zincking, 392 
solution for coating of, 
with bronze, 292 

YELLOW brass, 280 
-brown shades on zinc, 481 
color on bronze articles, 476,477 

silvered articles, 332 
prussiate of potash, 506, 507 

yAPON, 487 

/, Zilken's solution for tinning, 388 
Zinc alloys, production of, by the 
galvanic method, 396 
amalgamation of, 36, 37 
articles, copper bath for, 263, 264 
nickel bath for, 195 
pickling of, 163 
bath for brassing. 284 
baths, 391-393 

brassed, brown black color on, 476 
bronzing on, 481 
carbonate, 508, 509 
castings, nickel bath for, 195 



560 



INDEX. 



Zinc castings, treatment of, 148 
chloride, 501 

and ammonium chloride, 502 
qualities of, 1 74 
coloring of, 479-481 
cyanide, 506 
deposition of, 390-396 
gray coating on, 480.481 

yellow, brown to black colors 
upon, 480 
in brass baths, determination of, 
by electrolysis, 290, 
291 
volumetric determin- 
ation of, 291 
plates, coating of, with a thin but 

hard layer of copper, 272 
-plating, execution of, 392-395 
of wrought-iron objects, gird- 
ers L-iron, T-irou, etc., 
393-395 
properties of, 390, 391 
red-brown shades on, 481 
. scratch-brushing of, 157 



Zinc sheet, anodes used in nickeling, 
235 
black streaks and stains in 

nickeling, 235, 236 
brassing of, 233, 234 
cleansing of, 232, 233 
coppering of, 234, 271 
nickel bath for, 195 
nickeling of, 221-236 
preliminary grinding and 

polishing of, 222 
prevention of the peeling off 
of the nickel deposit from, 
233, 234 
treatment of, 148 
vats for nickeling, 234, 235 
sulphate, 511 
-tin alloy, deposition of, 396 

-nickel alloy, deposition of, 
396 
yellow-brown shades on, 481 
Zone, neutral, 11 

Zosimus, reduction of copper from its 
solution by iron described by, 1 



The Hanson &; Van Winkle Co., Newark, N. J., U. S.. A. 



ELECTROPLATING OUTFITS 



FOR 



Gold, Silver, Nickel, Copper, Etc 



Just a Word about Dynamos. 

Did you know that all the early experi- 
ments and improvements in Dynamos were 
made with a view of perfecting an electrical 
machine for plating, and that this success 
was the forerunner of all the magnificent 
Dynamo machines for other purposes in 
such general use to-day? 

In 1876 we began manufacturing the 

" Weston" Dynamo 
for electro-plating. 
This was the first 
machine in the mar- 
ket. It met with 
pronounced success, 
and to it can be 
traced the sudden 
development of electro-plating and electro- 
typing. Many of these machines are still 
in use. 

1 




The Hanson & Van Winkle Co., Newark, N. J., U. S. A. 




In 1885 we 
brought out the 
" Little Wonder" 
Dynamo. It be- 
came very popular. 
Over one thousand 

were sold. 
In 1886 we be- 
gan manufacturing 
the "Wonder" 
Dynamo. It em- 
bodied many new 
improvements, and 
we thought then 
that we had reached perfection. 

In 1 89 1 electrical science had devel- 
oped so many en- 
tirely new features, 
that in order to 
maintain our emi- 





nent position as 
leaders in the pro- 
duction of plating 

machines, we brought out our H. & V. W. 

Dynamo. It embodied every late idea, 

and has had a remarkable sale. 

(On the following page we show our new Iron Clad Dynamo. This 
also marks a new era in plating dynamos.) 



The Hanson 8z Van "Winkle Co., Newark, N. J., U. S. A. 




If You are Interested 

in Electro-plating, Electrotyping, Electro-refining of Metals or 
other Electro-chemical operations, you will naturally feel in- 
terested in anything that tends to bring these industries to the 
highest stage of development. 

In Introducing 

this new dynamo to your notice, we feel that we are urging the 
claims of a machine which will materially aid you in reaching 
that point. 

Many 

who have only used the old style machines have no idea of the 
improvements that have recently been made in this class of dy- 
namos; improvements that save time, money, labor and trouble. 

There are Several 

dynamos which are marked improvements on the old style of 
machines, but the new Iron Clad, while embracing all the 
good points found in other modern machines, has several 
improvements distinctively its own, and is the result of years 
of experimenting; there are no unusual number of brushes as 
in some other Dynamos, in some requiring 24 to 36 brushes 
to wear the Commutator and the patience of the plater. 



The Hanson & Van "Winkle Co., Newark, N. J., U. S. A. 



o — o — o 




o — o — o 



CAST 
ANODES 



OF ALL 



MEfkLS 

SIZE. 



M>» 



o — o — o 



Nickel: 

We are first hands in nickel and 
other metals, and the [largest 
manufacturers of the various 
Metallic Salts, of Nickel, Silver, 
Copper and Gold, and of 
Cyanide of Potassium. 

Plating Solutions : 

We furnish Concentrated Plat- 
ing Solutions of Silver, Gold, 
Copper, Nickel, Brass, etc. 

Batteries 

of all kinds. Our No. 1H.& 
V. W. Battery has had a larger 
sale than any other for Electro- 
Plating and experimental work. 

Jj-nod.es : 

Our Cast Nickel Anodes are 
standard for whitest results. 
Anodes of Nickel, Silver, 
Gold, Electro-deposited Cop- 
per, Brass, etc. Nickel castings. 



Tanks : 

Porcelain-lined, 



Iron, Wood. 



Slate, etc. , for all purposes. 

Lacquers : 

Patent Celluloid Lacquers for 
metal, paper, etc. Gold and 
colored Lacquers. 

Chemical Solution : 

For removing sand, scale, etc;., 
from castings, etc. 



The Hanson <fe Van Winkle Co., Newark, N. J., U. S. A. 



No. 7. Polishing and Buffing Lathe. 



Dimensions of Stand 




Size of base, 17x20 // . 
Size of top, 9xl2 // . 
Height of stand, 27 // . 
Weight of stand, 150 lbs 
Length of bearings, 6". 
Weight of lathe, 120 lbs. 



Dimensions of Lathe. 

Base, 9X12". 

Height from base to center 

of spindle, 39J". 
Diana, of spindle in boxes, 

Diam. of spindle between 

flanges, \\ f/ . 
Length of spindle, 52^. 
Size of pulley, 5x5". 



Spindle, 52" Long. Either A\" or 1" between Flanges. 

This Lathe is designed especially for bicycle manufacturers, although just as 
good for other classes of metal polishers. Lathes built on similar lines have been 
on the market for years, but in this machine we have designed new features not 
found in any other lathe. These improvements are the result of suggestions made 
by practical polishers, who fully understand what is required in a lathe for this 
work. A description in detail seems unnecessary, and the lathe must be seen or 
used to be appreciated. 

The boxes in this lathe are the best feature. They are self-lubricating, and can 
be adjusted in a moment to take up wear. With these boxes it is not necessary to 
remove the spindle from machine, nor is it necessary to take the boxes off to be 
planed or rebabbitted. Every practical mechanic will realize the time and annoy- 
ance saved by such a device. 

The pulley is made with flanges to prevent belt from slipping against frame 
when in use on heavy work. Lathe head and column are hollow, enabling them 
to be belted from the floor below if desired. 



The Hanson & Van Winkle Co., Newark, N. J., U. S. A. 



We manufacture a complete line of 



GRINDING, 
Polishing and Buffing Machines, 



and all the 



Various Wheels and Buffs and Grinding 
and Polishing Material. 




FELT VIENNA LIME 

COMPRESS CARBORUNDUM 

EMERY WOOD 

CROCUS SHEEPSKIN 

WALRUS ROUGE 

PAPER PUMICE 



The Hanson & Van Winkle Co., Newark, N. J., U. S: A. 



POLISHING SUPPLIES. 




TRIPOLI COMPOSITION. 

Tripoli Composition is especially adapted for cutting down and 
polishing Brass, Bronze, Britannia, and other metals preparatory 
to plating. 

Standard Tripoli Composition, O. S. for cutting and polishing, . per lb. 
" " " M, very greasy, .... lm 

" " " No. 6, hard and fast cutting, . " 

" " " H, very fast cutting, ... " 

" " " No. 9, similar to O. S., slightly sharper, " 

CROCUS COMPOSITION. 

Crocus Composition is largely used by stove manufacturers and 
others desiring to produce smooth finished surface on cast iron and 
steel. 



A, greasy, fast cutting, .... 

F. F. , dry and fast cutting, . . . . 

S, dry and fast cutting, .... 

O. S., very finest grade of this material, 
Emery Cake, ...... 

Emery Paste, ...... 

English Crocus, powdered, in kegs and casks, 

7 



per lb. 



The Hanson & Van Winkle Co., Newark, N. J., U. S. A. 



POLISHING SET. 




No.20fl 
Complete Box of Polishing Tools and Powders for small work . . $3.00 
When ordered with No. 22 or 24 Lathe, $2.00, with samples of Lacquer. 

8 



The Hanson & Van "Winkle Co., Newark, N. J., U. S. A. 



XXX BUFFI WG COMPOUND. 

For polishing and coloring all metals where the higher color is 
required, with the greatest economy of time, and especially for 
work that is engraved or ornamented where rouge is objectionable. 

Put up in cakes similar to Tripoli . . . ;^ per lb. 

VIENNA LIME. 




We are the largest importers of this article, and furnish it both 
in lump and powder, and send full instructions for getting best 
results. There is an increasing demand for this article for nickel 
and other work, and we are paying special attention to the quality. 

VIENNA LIME COMPOSITION- 





m **%&m,m* 



V»A UMLjCOMPoSiiKm 



VA * WJNKLE 




This is a very fine coloring material made from uniformly bolted 
Vienna Lime, and is highly recommended where white results are 
required. 

Put up in square cakes wrapped in paraffined paper, and sealed 
air-tight. 



The Hanson & Van Winkle Co., Newark, N. J., U. S. A. 




Our 184 page Catalogue mailed on application to any 
address in the world. 



The Hanson & Van Winkle Co., 



MANUFACTORY AND OFFICES: 



219 & 221 MARKET STREET, 



Newark, N. J., U. 5. A, 



NEW YORK OFFICE 
136 Liberty Street. 



WESTERN BRANCH : 
35 Sr 37 S. Canal St., Chicago, III. 

13 St. Paul Square, Birmingham, England. 

10 



O-A.T-^LLOa-TJS 

OF 

practical and Scientific Boo^ 

PUBLISHED BY 

Henry Carey Baird & Co. 

INDUSTRIAL PUBLISHERS, BOOKSELLERS AND IMPORTERS. 

810 Walnut Street, Philadelphia. 



©S~ Any of the Books comprised in this Catalogue will be sent by mail, free d 
postage, to any address in the world, at the publication prices, 

&&*■ A Descriptive Catalogue, 90 pages, 8vo., will be sent free and free of postage c 
to any one in any part of tbe world, who will furnish his address, 

3S£* Wbere not otherwise stated, all of the Books in this Catalogue are bound 
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AMATEUR MECHANICS' WORKSHOP: 

A treatise containing plain and concise directions for the manipula- 
tion of Wood and Metals, including Casting, Forging, Brazing, 
Soldering and Carpentry. By the author of the " Lathe and Its 
Uses." Seventh edition. Illustrated. 8vo. . . . $2.50 

ANDES.— Animal Fats and Oils: 

Their Practical Production. Purification and Uses; their Properties, 
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ANDES.— Vegetable Fats and Oils : 

Their Practical Preparation, Purification and Employment; their 
Properties, Adulteration and Examination. 94 illustrations. 8vo. 

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ARLOT.— A Complete Guide for Coach Painters : 

Translated from the French of M. Arlot, Coach Painter, for 
eleven years Foreman of Painting to M. Eherler, Coach Maker, 
Paris. By A. A. Fesqtjet, Chemist and Engineer. To which is 
added an Appendix, containing Informati^p '-esoecting the Materials 
and the Practice of Coach and Car Painting %..xi Varnishing in the 
United States and Great Britain- J2mo. . . . $1.25 

(0 



HENRY CAREY BAIRD & CO.'S CATALOGUE. 



ARMENGAUD, AMOROUX, AND JOHNSON.— The Practi- 
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chinist's and Engineer's Drawing Companion : 

Forming a Complete Course of Mechanical Engineering and Archi- 
tectural Drawing. From the French of JVL Armengaud the elder, 
Prof, of Design in the Conservatoire of Arts and Industry, Paris, and 
MM. Armengaud the younger, and Amoroux, Civil Engineers. Re- 
written and arranged with additional matter and plates, selections from 
and examples of the most useful and generally employed mechanism 
of the day. By William Johnson, Assoc. Inst. C. E. Illustrated 
by fifty folio steel plates, and fifty wood-cuts. A new edition, 4*0,, 

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ARMSTRONG.— The Construction and Management of Steam 
Boilers : 
By R. Armstrong, C. E. With an Appendix by Robert Mallet, 
C. E., F. R. S. Seventh Edition. Illustrated. 1 vol. i2mo. .60 

ARROWSMITH.— Paper-Hanger's Companion : 

A Treatise in which the Practical Operations of the Trade are 
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Papering; Preventives against the Effect of Damp on Walls; the 
various Cements and Pastes Adapted to the Several Purposes 01 
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\SHTON. — The Theory and Practice of the Art of Designing 
Fancy Cotton and Woollen Cloths from Sample : 

Giving full instructions for reducing drafts, as well as the methods of 
spooling and making out harness for cross drafts and finding any re- 
quired reed; with calculations and tables of yarn. By FREDERIC T. 
Ashton, Designer, West Pittsfield, Mass. With fifty-two illustrations. 
One vol. folio $S-°° 

ASKINSON. — Perfumes and their Preparation : 

A Comprehensive Treatise on Perfumery, containing Complete 
Directions for Making Handkerchief Perfumes, Smelling-Salts, 
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Articles. By G. W. Askinson. Translated from the German by IsiDOR 
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BRONGNIART. — Coloring and Decoration of Ceramic Ware. 
8vo $2.00 

BAIRD.— The American Cotton Spinner, and Manager's and 
Carder's Guide: 
A Practical Treatise on Cotton Spinning ; giving the Dimensions and 
Speed of Machinery, Draught and Twist Calculations, etc.; with 
notices of recent Improvements: together with Rules and Examples 
tor making changes in the sizes and numbers of Roving and Yarn. 
Compiled from the papw rf the late Robert H. Baird. i2mo. 



HENRY CAREY BAIRD & CO.'S CATALOGUE. 



3 AIRD.— Standard Wages Computing Tables : 

An Improvement in all former Methods of Computation, so arranged 
that wages for days, hours, or fractions of hours, at a specified rate 
per day or hour, may be ascertained at a glance. By T. Spangler 
Baird. Oblong folio ....... $5.00 

SAKER. — Long-Span Railway Bridges: 
Comprising Investigations of the Comparative Theoretical and 
Practical Advantages of the various Adopted or Proposed Type 
Systems of Construction; with numerous Formulae and Tables. By 

B. Baker. i2mo. $1.00 

BAKER.— The Mathematical Theory of the Steam-Engine : 
With Rules at length, and Examples worked out for the use of 
Practical Men. By T. Baker, C. E., with numerous Diagrams. 
Sixth Edition, Revised by Prof. J. R. Young. i2mo. . 75 

BARLOW. — The History and Principles of Weaving, by 
Hand and by Power : 
Reprinted, with Considerable Additions, from "Engineering," with 
a chapter on Lace-making Machinery, reprinted from the Journal of 
the " Society of Arts." By Alfred Barlow. With several hundred 
illustrations. 8vo., 443 pages ..... (Scarce.) 

BARR. — A Practical Treatise on the Combustion of Coal: 
Including descriptions of various mechanical devices for the Eco- 
nomic Generation of Heat by the Combustion of Fuel, whether solid, 
liquid or gaseous. 8vo. ....... $2.50 

BARR. — A Practical Treatise on High Pressure Steam Boilers : 
Including Results of Recent Experimental Tests of Boiler Materials, 
together with a Description of Approved Safety Apparatus, Steam 
Pumps, Injectors and Economizers in actual use. By Wm. M. Barr. 
204 Illustrations. 8vo. . ..... $3.00 

3AUERMAN.— A Treatise on the Metallurgy of Iron : 
Containing Outlines of the History of Iron Manufacture, Methods of 
Assay, and Analysis of Iron Ores, Processes of Manufacture of Iron 
and Steel, etc., etc. By H. Bauerman, F. G. S., Associate of the 
Royal School of Mines. Fifth Edition, Revised and Enlarged. 
Illustrated with numerous Wood Engravings from Drawings by J. B. 

Jordan. i2mo $2.oc 

BRANNT.— The Metallic Alloys: A Practical Guide 

For the Manufacture of all kinds of Alloys, Amalgams, and Solders, 
used by Metal- Workers; together with their Chemical and Physical 
Properties and their Application in the Arts and the Industries; with 
an Appendix on the Coloring of Alloys and the Recovery of Waste 
Metals. By William T. Brannt. 34 Engravings. A New, Re- 
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BEANS. — A Treatise on Railway Curves and Location of 
Railroads : 
By E. W. Beans, C. E. Illustrated. i2mo. Tucks . $1.50 
BECKETT.— A Rudimentary Treatise on Clocks, and Watches 
and Bells : 
By Sir Edmund Beckett, Bart., LL. D., Q. C. F. R. A. S. With 
numerous illustrations. Seventh Edition, Revised and Enlarged. 
S2mo $i.8o 



HENRY CAREY BAIRD & CO.'S CATALOGUE. 



BELL. — Carpentry Made Easy: 

Or, The Science and Art of Framing on a New and Improved 
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Frames, Mill Frames, Warehouses, Church Spires, etc. Comprising 
also a System of Bridge Building, with Bills, Estimates of Cost, and 
valuable Tables. Illustrated by forty-four plates, comprising nearly 
200 figures. By William E. Bell, Architect and Practical Builder. 
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BEMROSE. — Fret-Cutting and Perforated Carving: 

With fifty-three practical illustrations. By W. Bemrose, Jr. I vol. 
quarto $2.5® 

BEMROSE. — Manual of Buhl-work and Marquetry: 

With Practical Instructions for Learners, and ninety colored designs. 
By W. Bemrose, Jr. i vol. quarto .... $3.00 

BEMROSE.— Manual of Wood Carving: 

With Practical Illustrations for Learners of the Art, and Original and 
Selected Designs. By William Bemrose, Jr. With an Intro- 
duction by Llewellyn Jewitt, F. S. A., etc. With 128 illustra- 
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BILLINGS.— Tobacco : 

Its History, Variety, Culture, Manufacture, Commerce, and Various 
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8IRD. — The American Practical Dyers' Companion: 
Comprising a Description of the Principal Dye-Stuffs and Chemicals 
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with the best American, English, French and German processes for 
Bleaching and Dyeing Silk, Wool, Cotton, Linen, Flannel, Felt. 
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170 Dyed Samples of Raw Materials and Fabrics. By F. J. Bird, 
Practical Dyer, Author of " The Dyers' Hand-Book." 8vo. ^7.50 

BLINN. — A Practical Workshop Companion for Tin, Sheet- 
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Containing Rules for describing various kinds of Patterns used by 
Tin, Sheet-Iron and Copper-plate Workers; Practical Geometry; 
Mensuration of Surfaces and Solids ; Tables of the Weights of 
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HENRY CAREY BAIRD & CO.'S CATALOGUE. 



BOOTH, — Marble Worker's Manual : 

Containing Practical Information respecting Marbles in general, theif 
Cutting, Working and Polishing ; Veneering of Marble ; Mosaics ; 
Composition and Use of Artificial Marble, Stuccos, Cements, Receipts, 
Secrets, etc., etc. Translated from the French by M. L. Booth. 
With an Appendix concerning American Marbles. i2mo., cloth $1.50 
BOOTH and MORFIT. — The Encyclopaedia of Chemistry, 
Practical and Theoretical : 
Embracing its application to the Arts, Metallurgy, Mineralogy, 
Geology, Medicine and Pharmacy. By James C. Booth, Melter 
and Refiner in the United States Mint, Professor of Applied Chem- 
istry in the Franklin Institute, etc., assisted by Campbell Morfit, 
author of " Chemical Manipulations," etc. Seventh Edition. Com- 
plete in one volume; royal 8vo., 978 pages, with numerous wood-cuts 
and other illustrations (Scarce.) 

BRAMWELL.— The Wool Carder's Vade-Mecum* 

A Complete Manual of the Art of Carding Textile Fabrics. By W< 
C. Bramwell. Third Edition, revised and enlarged. Illustrated. 
Pp. 400. i2mo $2.50 

BRANNT.— A Practical Treatise on Animal and Vegetable 
Fats and Oils : 
Comprising both Fixed and Volatile Oils, their Physical and Chem- 
ical Properties and Uses, the Manner of Extracting and Refining 
them, and Practical Rules for Testing them; as well as the Manufac- 
ture of Artificial Butter and Lubricants, etc., with lists of American 
Patents relating to the Extraction, Rendering, Refining, Decomposing, 
and Bleaching of Fats and Oils. By William T. Brannt, Editor 
of the " Techno-Chemical Receipt Book." Second Edition, Revised 
and in a great part Rewritten. Illustrated by 302 Engravings. In 
Two Volumes. 1304 pp. 8vo. ..... $10.00 

BRANNT.— A Practical Treatise on the Manufacture of Soap 
and Candles : 
Based upon the most Recent Experiences in the Practice and Science ; 
comprising the Chemistry, Raw Materials, Machinery, and Utensils 
and Various Processes of Manufacture, including a great variety of 
formulas. Edited chiefly from the German of Dr. C. Deite, A. 
Engelhardt, Dr. C. Schaedler and others; with additions and lists 
of American Patents relating to these subjects. By Wm. T. Brannt. 
Illustrated by 163 engravings. 677 pages. 8vo. . . $J-S° 

BRANNT.— India Rubber, Gutta Percha and Balata : 

Occurrence, Geographical Distribution, and Cultivation, Obtaining 
and Preparing the Raw Materials, Modes of Working and Utilizing 
them, Including Washing, Maceration, Mixing, Vulcanizing, Rubber 
and Gutta-Percha Compounds, Utilization of Waste, etc. By WILL- 
IAM T. Brannt. Illustrated. i2mo. (1900.) . . $3.00 



HENRY CAREY BAIRD & CO.'S CATALOGUE. 



BRANNT— WAHL.- The Techno- Chemical Receipt Books 

Containing several thousand Receipts covering the latest, most «f» 
portant, and most useful discoveries in Chemical Technology, an< 
their Practical Application in the Arts and the Industries. Editec 
chiefly from the German of Drs. Winckler, Eisner, Heintze, Mier 
zinski, Jacobsen, Roller, and Heinzerling, with additions by Wm. '1. 
Brannt and Wm. H. Wahl, Ph. D. Illustrated by 78 engravings. 
I2Jiio. 495 pages . . . . . _ #2.00 

BROWN. — Five Hundred and Seven Mechanical Movements: 
Embracing all those which are most important in Dynamics, Hy- 
draulics, Hydrostatics, Pneumatics, Steam-Engines, Mill and othet 
Gearing, Presses, Horology and Miscellaneous Machinery; and in- 
cluding many movements never before published, and several of 
which have only recently come into use. By Henry T. Brown 
l2mo. .......... $1.00 

BUCKM ASTER.— The Elements of Mechanical Physics: 
By J. C. BUCKMASTER. Illustrated with numerous engravings. 
i2mo . $1.00 

BULLOCK.— The American Cottage Builder : 

A Series of Designs, Plans and Specifications, from $200 to $20,000, 
for Homes for the People ; together with Warming, Ventilation, 
Drainage, Painting and Landscape Gardening. By John Bullock, 
Architect and Editor of "The Rudiments of Architecture and 
Building," etc., etc. Illustrated by 75 engravings. 8vo. $2.50 

BULLOCK. — The Rudiments of Architecture and Building: 
For the use of Architects, Builders, Draughtsmen, Machinists, En- 
gineers and Mechanics. Edited by John Bullock, author of " The 
American Cottage Builder." Illustrated by 250 Engravings. 8vo.$2.5o 

BURGH. — Practical Rules for the Proportions of Modern 
Engines and Boilers for Land and Marine Purposes. 
By N. P. Burgh, Engineer. i2mo. . . . . $1.50 

BYLES.— Sophisms of Free Trade and Popular Political 
Economy Examined. 
By a Barrister (Sir John Barnard Byles, Judge of Common 
Fleas). From the Ninth English Edition, as published by the 
Manchester Reciprocity Association. i2mo. . . . $1.25 

BOWMAN. — The Structure of the Wool Fibre in its Relation 
to the Use of Wool for Technical Purposes : 
Being the substance, with additions, of Five Lectures, deliverea at 
the request of the Council, to the members of the Bradford Technical 
College, and the Society of Dyers and Colovists. By F. H. Bow- 
man, D. Sc, F. R. S. E., F. L. S. Illustrated by 32 engravings. 
8vo. ........... #5.00 

BYRNE. — Hand-Book for the Artisan, Mechanic, and Engi- 
neer: 
Comprising the Grinding and Sharpening of Cutting Tools, Abi = - . = 
Processes, Lapidary Work, Gem and Glass Engraving, Varnishing 
and Lackering, Apparatus, Materials and Processes for Grinding and 



HENRY CAREY BAIRD & CO.'S CATALOGUE. 



Polishing, etc. By Oliver Byrne. Illustrated by 185 wood en- 
gravings. 8vo. #5.oc 

8YRNE.— Pocket-Book for Railroad and Civil Engineers: 

Containing New, Exact and Concise Methods for Laying out Railroad 
Curves, Switches, Frog Angles and Crossings ; the Staking out of 
work ; Levelling ; the Calculation of Cuttings ; Embankments ; Earth- 
work, etc. By Oliver Byrne. i8mo., full bound, pocket-book 
form #1.50 

BYRNE.— The Practical Metal- Worker's Assistant : 
Comprising Metallurgic Chemistry; the Arts of Working all Metals 
and Alloys ; Forging of Iron and Steel ; Hardening and Tempering; 
Melting and Mixing; Casting and Founding ; Works in Sheet Metal; 
the Processes Dependent on the Ductility of the Metals; Soldering; 
and the most Improved Processes and Tools employed by Metal- 
workers. With the Application of the Art of Electro-Metallurgy to 
Manufacturing Processes ; collected from Original Sources, and from 
the works of Holtzapffel, Bergeron, Leupold, Piumier, Napier, 
Scoffern, Clay, Fairbairn and others. By Oliver Byrne. A new, 
revised and improved edition, to which is added an Appendix, con- 
taining The Manufacture of Russian Sheet-Iron. By John Percy, 
M. D., F. R. S. The Manufacture of Malleable Iron Castings, and 
Improvements in Bessemer Steel. By A. A. Fesquet, Chemist and 
Engineer. With over Six Hundred Engravings, Illustrating every 
Branch of the Subject. 8vo $5-OG 

BYRNE.— The Practical Model Calculator: 

For the Engineer, Mechanic, Manufacturer of Engine Work, NavaJ 
Architect, Miner and Millwright. By Oliver Byrne. 8vo., nearly 
600 pages ... ...... $3.00 

CABINET MAKER'S ALBUM OF FURNITURE. 
Comprising a Collection of Designs for various Styles of Furniture. 
Illustrated by Forty-eight Large and Beautifully Engraved Plates. 
Oblong, 8vo . $1.50 

^ALLINGHAM. — Sign Writing iind Glass Embossing: 

A Complete Practical Illustrated Manual of the Art. By JAMES 
Callingham. To which are added Numerous Alphabets and the 
Art of Letter Painting Made Easy. By James C. Badenoch. 258 
pages. 121110. ........ $1 50 

2AMPIN. — A Practical Treatise on Mechanical Engineering: 
Comprising Metallurgy, Moulding, Casting, Forging, Tools, Work< 
shop Machinery, Mechanical Manipulation, Manufacture of Steam- 
Engines, etc. With an Appendix on the Analysis of Iron and Iron 
Ores. By Fpancis Campin, C. E. To which are added, Observations 
on the Construction of Steam Boilers, and Remarks upon Furnaces 
used for Smoke Prevention ; with a Chapter on Explosions. B>- R. 
Armstrong, C. E., and John Bourne. (Scarce.) 



HENRY CAREY BAIRD & CO.'S CATALOGUE. 



CAREY.— A Memoir of Henry C. Carey. 

By Dr. Wm. Elder, With a portrait. 8vo., cloth . . 75 

CAREY.— The Works of Henry C. Carey : 

Harmony of Interests : Agricultural, Manufacturing and Commer- 
cial. 8vo. . . $1.25 

Manual of Social Science. Condensed from Carey's " Principles 
of Social Science." By Kate McKean. i vol. i2mo. . #2.00 
Miscellaneous Works. With a Portrait. 2 vols. 8vo. $10.00 

Past, Present and Future. 8vo $2.50 

Principles of Social Science. 3 volumes, 8vo. . . $7.50 
The Slave-Trade, Domestic and Foreign; Why it Exists, and 
How it may be Extinguished (1853). 8vo. . . . $2.00 
The Unity of Law : As Exhibited in the Relations of Physical, 
Social, Mental and Moral Science (1872). 8vo. . . $2.50 

CLARK. — Tramways, their Construction and Working : 

Embracing a Comprehensive History of the System. With an ex' 
haustive analysis of the various modes of traction, including horse- 
power, steam, heated water and compressed air; a description of the 
varieties of Rolling stock, and ample details of cost and working ex- 
penses. By D. Kinnear Clark. Illustrated by over 200 wood 
engravings, and thirteen folding plates. I vol. 8vo. . $7.50 

COLBURN.— The Locomotive Engine : 

Including a Description of its Structure, Rules for Estimating its 
Capabilities, and Practical Observations on its Construction and Man- 
agement. By Zerah COLBURN. Illustrated. 121110. . $l.oa 

COLLENS.— The Eden of Labor; or, the Christian Utopia. 
By T. Wharton Collens, author of " Humanics," "The Historj 
of Charity," etc. i2mo. Paper cover, $1.00; Cloth . $1.25 

200LEY. — A Complete Practical Treatise on Perfumery : 
Being a Hand-book of Perfumes, Cosmetics and other Toilet Articiet 
With a Comprehensive Collection of Formulae. By Arnold 
Cooley. i2mo $1.50 

COOPER.— A Treatise on the use of Belting for the Trant 
mission of Power. 
With numerous illustrations of approved and actual methods of ar 
ranging Main Driving and Quarter Twist Belts, and of Belt Fasten 
ings. Examples and Rules in great number for exhibiting and cal 
culating the size and driving power of Belts. Plain, Particular and 
Practical Directions for the Treatment, Care and Management o 
Belts. Descriptions of many varieties of Beltings, together witn 
chapters on the Transmission of Power by Ropes; by Iron and 
Wood Frictional Gearing; on the Strength of Belting Leather; and 
on the Experimental Investigations of Morin, Briggs, and others. Bj> 
John H. Cooper, M. E. 8vo $3-5 c 

CRAIK. — The Practical American Millwright and M^ler. 

By David Craik, Millwright. Illustrated by numerous rood en 
gravings and two folding plates. 8vo. , (Scarce.) 



HENRY CAREY BAIRD & CO.'S CATALOGUE. 



CROSS.— The Cotton Yarn Spinner: 

Showing how the Preparation should be arranged for Different 
Counts of Yarns by a System more uniform than has hitherto been 
practiced; by having a Standard Schedule from which we make all 
our Changes. By Richard Cross. 122 pp. i2mo. . 75 

CRISTIANI.— A Technical Treatise on Soap and Candles: 
With a Glance at the Industry of Fats and Oils. By R. S. Cris- 
TIANI, Chemist. Author of " Perfumery and Kindred Arts." Illus- 
trated by 176 engravings. 581 pages, 8vo. $15.00 

COURTNEY.— The Boiler Maker's Assistant in Drawing, 
Templating, and Calculating Boiler Work and Tank 
Work, etc. 
Revised by D. K. Clark. 102 ills. Fifth edition. . . 80 
COURTNEY.— The Boiler Maker's Ready Reckoner: 

With Examples of Practical Geometry and Templating. Revised by 
D. K. Clark, C. E. 37 illustrations. Fifth edition. • $1.60 

DAVIDSON. — A Practical Manual of House Painting, Grain- 
ing, Marbling, and Sign- Writing: 
Containing full information on the processes of House Painting in 
Oil and Distemper, the Formation of Letters and Practice of Sign- 
Writing, the Principles of Decorative Art, a Course of Elementary 
Drawing for House Painters, Writers, etc., and a Collection of Useful 
Receipts. With nine colored illustrations of Woods and Marbles, 
and numerous wood engravings. By Ellis A, Davidson. i2mo. 

$2.00 

DAVIES.— A Treatise on Earthy and Other Minerals and 

Mining: 
By D. C. Davies, F. G. S., Mining Engineer, etc. Illustrated by 
76 Engravings. l2mo. . . . . . . . $5 00 

DAVIES. — A Treatise on Metalliferous Minerals and Mining: 
By D. C. Davies, F. G. S , Mining Engineer, Examiner of Mines, 
Quarries and Collieries. Illustrated by 148 engravings of Geological 
Formations, Mining Operations and Machinery, drawn from the 
practice of all parts of the world. Fifth Edition, thoroughly Revised 
and much Enlarged by his son, E. Henry Davies. 121110., 524 
pages ....... . $5-00 

DAVIES.— A Treatise on Slate and Slate Quarrying: 

Scientific, Practical and Commercial. By D, C. Davies, F. G S , 
Mining Engineer, etc. With numerous illustrations and folding 
plates. !2mo. $1.20 

DAVIS. — A Practical Treatise on the Manufacture of Brick, 

Tiles and Terra-Cotta : 

Including Stiff Clay, Dry Clay, Hand Made, Pressed or Front, and 

Roadway Paving Brick, Enamelled Brick, with Glazes and Colors, 

Fire Brick and Blocks, Silica Brick, Carbon Brick, Glass Pots, Re- 



xo HENRY CAREY BAIRD & CO.'S CATALOGUE. 

torts, Architectural Terra-Cotta, Sewer Pipe, Drain Tile, Glazed and 
Unglazed Roofing Tile, Art Tile, Mosaics, and Imitation of Intarsia 
or Inlaid Surfaces. Comprising every product of Clay employed in 
Architecture, Engineering, and the Blast Furnace. With a Detailed 
Description of the Different Clays employed, the Most Modern 
Machinery, Tools, and Kilns used, and the Processes for Handling, 
Disintegrating, Tempering, and Moulding the Clay into Shape, Dry- 
ing, Setting, and Burning. By Charles Thomas Davis. Third Edi- 
tion. Revised and in great part rewritten. Illustrated by 261 
engravings. 662 pages . . . . . . . $5 00 

DAVIS. — A Treatise on Steam-Boiler Incrustation and Meth- 
ods for Preventing Corrosion and the Formation of Scale: 
By Charles T. Davis. Illustrated by 65 engravings. 8vo. $2.00 

DAVIS.— The Manufacture of Paper: 

Being a Description of the various Processes for the Fabrication, 
Coloring and Finishing of every kind of Paper, Including the Dif- 
ferent Raw Materials and the Methods for Determining their Values, 
the Tools, Machines and Practical Details connected with an intelli- 
gent and a profitable prosecution of the art, with special reference to 
the best American Practice. To which are added a History of Pa- 
per, complete Lists of Paper- Making Materials, List of American. 
Machines, Tools and Processes used in treating the Raw Materials, 
and in Making, Coloring and Finishing Paper. By Charles T. 
Davis. Illustrated by 156 engravings. 608 pages, 8vo. $6.00 

DAVIS. — The Manufacture of Leather: 

Being a Description of all the Urocesses for the Tanning and Tawing 
with Bark, Extracts, Chrome and all Modern Tannages in General 
Use, and the Currying, Finishing and Dyeing of Every Kind of Leather ; 
Including the Various Raw Materials, the Tools, Machines, and all 
Details of Importance Connected with an Intelligent and Profitable 
Prosecution of the Art, with Special Reference to the Best American 
Practice. To which are added Lists of American Patents ( 1884-1897) 
for Materials, Processes, Tools and Machines for Tanning, Currying, 
etc. By Charles Thomas Davis. Second Edition, Revised, and 
in great part Rewritten. Illustrated by 147 engravings and 14 Sam- 
ples ol Quebracho Tanned and Aniline Dyed Leathers. 8vo, cloth, 
712 pages. Price $7-5° 

DAWIDOWSKY— BRANNT.— A Practical Treatise on the 

Raw Materials and Fabrication of Glue, Gelatine, Gelatine 

Veneers and Foils, Isinglass, Cements, Pastes, Mucilages, 

etc. : 

Based upon Actual Experience. By F. DAWIDOWSKY, Technical 

Chemist. Translated from the German, with extensive additions, 

including a description of the most Recent American Processes, by 

William T. Brannt, Graduate of the Royal Agricultural College 

of Eldena, Prussia. 35 Engravings. i2mo. . . . $2.50 

DE GRAFF.— The Geometrical Stair-Builders' Guide : 
Being a Plain Practical System of Hand-Railing, embracing all its 
necessary Details, and Geometrically Illustrated by twenty-two Steel 
Engravings; together with the use of the most approved principles 
of Practical Geometry. By Simon De Graff, Architect, (Scarce.) 



HENRY CAREY BAIRD & CO.'S CATALOGUE. n 

DE KONINCK— DIETZ.— A Practical Manual of Chemical 
Analysis and Assaying : 
As applied to the Manufacture of Iron from its Ores, and to Cast Iron, 
Wrought Iron, and Steel, as found in Commerce. By L. L. Dfi 
K.ONINCK, Dr. Sc, and E. Dietz, Engineer. Edited wilh Notes, by 
Robert Mallet, F. R. S., F. S. G., M. I. C. E., etc. American 
Edition, Edited with Notes and an Appendix on Iron Ores, by A. A. 
Fesquet, Chemist and Engineer. i2mo. . . . $1.50 

DUNCAN.— Practical Surveyor's Guide: 

Containing the necessary information to make any person of corm 
mon capacity, a finished land surveyor without the aid of a teacher 
By Andrew Duncan. Revised. 72 engravings, 214 pp. i2mo. $1.50 

DUPLAIS. — A Treatise on the Manufacture and Distillation 
of Alcoholic Liquors : 
Comprising Accurate and Complete Details in Regard to Alcohol 
from Wine, Molasses, Beets, Grain, Rice, Potatoes, Sorghum, Aspho 
del, Fruits, etc. ; with the Distillation and Rectification of Brandy; 
Whiskey, Rum, Gin, Swiss Absinthe, etc., the Preparation of Aro- 
matic Waters, Volatile Oils or Essences, Sugars, Syrups, Aromatic 
Tinctures, Liqueurs, Cordial Wines, Effervescing Wines, etc., the 
Ageing of Brandy and the improvement of Spirits, with Copioas 
Directions and Tables for Testing and Reducing Spirituous Liquors, 
et(\, etc. Translated and Edited from the French of MM. Duplais, 
By M. McKennie, M. D. Illustrated. 743 pp. 8vo. $15.00 

DYER AND COLOR-MAKER'S COMPANION: 

Containing upwards of two hundred Receipts for making Colors, on 
the most approved principles, for all the various styles and fabrics now 
in evistence ; with the Scouring Process, and plain Directions for 
Preparing, Washing-off, and Finishing the Goods. l2mo. $ I OO 

EIDHERR.— The Techno-Chemical Guide to Distillation: 
A Hand-Book for the Manufacture of Alcohol and Alcoholic Liquors, 
including the Preparation of Malt and Compressed Yeast. Edited 
from the German of Ed. Eidherr. Fully illustrated. (In preparation.) 

EDWARDS. — A Catechism of the Marine Steam-Engine, 
For the use of Engineers, Firemen, and Mechanics. A Practical 
Work for Practical Men. By Emory Edwards, Mechanical Engi- 
neer. Illustrated by sixty-three Engravings, including examples of 
the most modern Engines. Third edition, thoroughly revised, with 
much additional matter. 1 2 mo. 414 pages . . . $2 00. 

EDWARDS. — Modern American Locomotive Engines, 
Their Design, Construction and Management. By EMORY EDWARDSt 
Illustrated i2mo #2.00 

EDWARDS. — The American Steam Engineer: 

Theoretical and Practical, with examples of the latest and most ap- 
proved American practice in the design and construction of Steam 
Engines and Boilers. For the use of engineers, machinists, boiler- 
takers, and engineering students. By Emory Edwards. Fully 
illustrated, 419 pages. i2mo. - $2.50 



12 HENRY CAREY BAIRD & CO.'S CATALOGUE. 

EDWARDS. — Modern American Marine Engines, Boilers, ani 
Screw Propellers, 

Their Design and Construction. Showing the Present Practice ot 
the most Eminent Engineers and Marine Engine Builders in the 
United States. Illustrated by 30 large and elaborate plates. 4to. $5.00 
EDWARDS.— The Practical Steam Engineer's Guide 

In the Design, Construction, and Management of American Stationary, 
Portable, and Steam Fire- Engines, Steam Pumps, Boilers, Injectors, 
Governors, Indicators, Pistons and Rings, Safety Valves and Steam 
Gauges. For the use of Engineers, Firemen, and Steam Users. By 
Emory Edwards. Illustrated by 119 engravings. 420 pages, 
l2mo $2 50 

EISSLER.— The Metallurgy of Gold : 
A Practical Treatise on the Metallurgical Treatment of Gold-Bear- 
ing Ores, including the Processes of Concentration and Chlorination, 
and the Assaying, Melting, and Refining of Gold. By M. Eissler. 

With 132 Illustrations. i2mo #7-5o 

EISSLER.— The Metallurgy of Silver : 

A Practical Treatise on the Amalgamation, Roasting, and Lixiviation 
of Silver Ores, including the Assaying, Melting, and Refining of 
Silver Bullion. By M. Eissler. 124 Illustrations. 336 pp. 

i2mo $4-25 

ELDER. — Conversations on the Principal Subjects of Political 
Economy. 

By Dr. William Elder. 8vo $2.50 

ELDER.— Questions of the Day, 

Economic and Social. By Dr. William Elder. 8vo. . #3.00 
ERNI AND BROWN.— Mineralogy Simplified. 

Easy Methods of Identifying Minerals, including Ores, by Means of 
the Blow-pipe, by Flame Reactions, by Humid Chemical Analysis, 
and by Physical Tests. By Henri Erni, A. M., M. D. Third Edi- 
tion, revised, re-arranged and with the addition of entirely new matter, 
including Tables for the Determination of Minerals by Chemical and 
Pyrognostic Characters, and by Physical Characters. By Amos P. 
Brown, E. M., Ph. D. 350 pp., illustrated by 96 engravings, pocket- 
book form, full flexible morocco, gilt edges . . . #2.50 
FAIRBAIRN.— The Principles of Mechanism and Machinery 
of Transmission * 
Comprising the Principles of Mechanism, Wheels, and Pulleys, 
Strength and Proportions of Shafts, Coupling of Shafts, and Engag 
ing and Disengaging Gear. By Sir William Fairbairn, Bait 
C. E. Beautifully illustrated by over 150 wood-cuts. In one 

Yolume, i2mo . . $2.00 

FLEMING. — Narrow Gauge Railways in America. 
A Sketch of their Rise, Progress, and Success. Valuable Statistics 
as to Grades, Curves, Weight of Rail, Locomotives, Cars, etc. By 

Howard Fleming. Illustrated, 8vo |i 00 

FORSYTH.— Book of Designs for Headstones, Mural, and 
oth&r Monuments : 
Containing 78 Designs. By James Forsyth. With an Introduction 
by Charles Boutell, M. A. 4 to., cloth . . • $3-5o 



HENRY CAREY BAIRD & CO.'S CATALOGUE. 13 



FRANKEL- HUTTER.— A Practical Treatise on the Manu» 
facture of Starch, Glucose, Starch-Sugar, and Dextrine: 

Based on the German of Ladislaus Von Wagner, Professor in the 
Royal Technical High School, Buda-Pest, Hungary, and other 
authorities. By Julius Frankel, Graduate of the Polytechnic 
School of Hanover. Edited by Robert Hutter, Chemist, Practical 
Manufacturer of Starch-Sugar. Illustrated by 58 engravings, cover- 
ing every branch of the subject, including examples of the most 
Recent and Best American Machinery. 8vo., 344 pp. . $3.50 

GARDNER.- The Painter's Encyclopaedia: 
Containing Definitions of all Important Words in the Art of Plain 
and Artistic Painting, with Details of Practice in Coach, Carriage, 
Railway Car, House, Sign, and Ornamental Painting, including 
Graining, Marbling, Staining, Varnishing, Polishing, Lettering, 
Stenciling, Gilding, Bronzing, etc. By Franklin B. Gardner. 
158 Illustrations. i2mo. 427 pp. . . . . . $2.00 

GARDNER.— Everybody's Paint Book: 

A Complete Guide to the Art of Outdoor and Indoor Painting. 38 
illustrations 121110, 183 pp . . $1.00 

GEE. — The Jeweller's Assistant in the Art of Working in 
Gold: 
A Practical Treatise foi Masters and Workmen. i2mo. . $3.00 

GEE.— The Goldsmith's Handbook : 

Containing full instructions for the Alloying and Working of Gold, 
including the Art of Alloying, Melting, Reducing, Coloring, Col- 
lecting, and Refining; the Processes of Manipulation, Recovery of 
Waste; Chemical and Physical Properties of Gold; with a New 
System of Mixing its Alloys ; Solders, Enamels, and other Useful 
Rules and Recipes. By George E. Gee. i2mo. . #1.25 

GEE. — The Silversmith's Handbook : 

Containing full instructions for the Alloying and Working of Silver, 
including the different modes of Refining and Melting the Metal; its 
Solders; the Preparation of Imitation Alloys; Methods of Manipula- 
tion ; Prevention of Waste ; Instructions for Improving and Finishing 
the Surface of the Work; together with other Useful Information and 
Memoranda. By George E. Gee. Illustrated. i2mo. Si. 25 

GOTHIC ALBUM FOR CABINET-MAKERS: 

Designs for Gothic Furniture. Twenty-three plates. Oblong $1.5° 

3RANT.-A Handbook on the Teeth of Gears : 
Their Curves, Properties, and Practical Construction. By George 
B. Grant. Illustrated. Third Edition, enlarged. 8vo. $1.00 

GREENWOOD.— Steel and Iron : 
Comprising the Practice and Theory of the Several Methods Pur- 
sued in their Manufacture, and of their Treatment in the Rolling- 
Mills, the Forge, and the Foundry. By William Henry Green* 
WOOD, F. C. S. With 97 Diagrams, 536 pages. i2mo. $1.75 



14 HENRY CAREY BAIRD & CO.'S CATALOGUE, 



GREGORY. — Mathematics for Practical Men : 

Adapted to the Pursuits of Surveyors, Architects, Mechanics, and 
Civil Engineers. By Olinthus Gregory. 8vo., plates #3.00 

GRISWOLD.— Railroad Engineer's Pocket Companion for thi 
Field : 
Comprising Rules for Calculating Deflection Distances and Angles, 
Tangential Distances and Angles, and all Necessary Tables for En 
gineers; also the Art of Levelling from Preliminary Survey to the 
Construction of Railroads, intended Expressly for the Young En- 
gineer, together with Numerous Valuable Rules and Examples. By 
W. Griswold. i2mo., tucks #l-5o 

GRUNER. — Studies of Blast Furnace Phenomena: 

By M. L. Gruner, President of the General Council of Mines 0$ 
France, and lately Professor of Metallurgy at the Ecole des Mines. 
Translated, with the author's sanction, with an appendix, by L. D. 
B. Gordon, F. R. S. E., F. G. S. 8vo. . . . #2.50 

Hand-Book of Useful Tables for the Lumberman, Farmer and 
Mechanic: 
Containing Accurate Tables of Logs Reduced to Inch Board Meas. 
ure, Plank, Scantling and Timber Measure ; Wages and Rent, by 
Week or Month; Capacity of Granaries, Bins and Cisterns; Land 
Measure, Interest Tables, with Directions for Finding the Interest on 
any sum at 4, 5, 6, 7 and 8 per cent., and many other Useful Tables. 
32 mo., boards. 186 pages .25 

HASERICK.— The Secrets of the Art of Dyeing Wool, Cotton 
and Linen, 
Including Bleachir.g and Coloring Wool and Cotton Hosiery and 
Random Yarns. A Treatise based on Economy and Practice. By 
E. C. Haserick. Illustrated by 323 Dyed Patterns of the Yarm 
or Fabrics. 8vo. $5*°0 

HATS AND FELTING : 

A Practical Treatise on their Manufacture. By a Practical Platter. 
Illustrated by Drawings of Machinery, etc. 8vo. . . #1.25 

HERMANN. — Painting oh Glass and Porcelain, and Enamel 
Painting: 
A Complete Introduction to the Preparation of all the Colors and 
Fluxes Used for Painting on Glass, Porcelain, Enamel, Faience and 
Stoneware, the Color Pastes and Colored Glasses, together with a 
Minute Description ot the Firing of Colors and Enamels, on the 
Basis of Personal Practical Experience of the Art up to Date. 18 
illustrations. Second edition. $4.0C 

HAUPT.— Street Railway Motors: 

With Descriptions and Cost of Plants and Operation of the Various 
Systems now in Use. UfXCi/' > #'75 



HENRY CAREY BAIRD & CO.'S CATALOGUE. 15 

HAUPT. — A Manual of Engineering Specifications and Con- 
tracts. 

By Lewis M. Haupt, C. E. Illustrated with numerous maps. 
328pp. 8vo $3 00 

HAUPT. — The Topographer, His Instruments and Methods. 
By Lewis M. Haupt, A. M., C. E. Illustrated with numerous 
plates, maps and engravings. 247 pp. 8vo. . . . $3.00 

HUGHES. — American Miller and Millwright's Assistant: 
By William Carter Hughes. i2mo $1.50 

HULME. — Worked Examination Questions in Plane Geomet- 
rical Drawing : 
For the Use of Candidates for the Royal Military Academy, Wool- 
wich; the Royal Military College, Sandhurst; the Indian Civil En- 
gineering College, Cooper's Hill ; Indian Public Works and Tele- 
graph Departments ; Royal Marine Li^ht Infantry ; the Oxford and 
Cambridge Local Examinations, etc. By F. Edward Hulme, F. L. 
S., F. S. A., Art-Master Marlborough College. Illustrated by 300 
examples. Small quarto <> $l»$o 

JERVIS.— Railroad Property: 

A Treatise on the Construction and Management of Railways 1 , 
designed to afford useful knowledge, in the popular style, to the 
holders of this class of property ; as well as Railway Managers, Offi 
cers, and Agents. By John B. Jervis, late Civil Engineer of the 
Hudson River Railroad, Croton Aqueduct, etc. i2mo., cloth $2.oc 

KEENE.— A Hand-Book of Practical Gauging: 
For the Use of Beginners, to which is added a Chapter on Distilla 
tion, describing the process in operation at the Custom-House for 
ascertaining the Strength of Wines. By James B. Keene, of H. M. 
Customs. 8vo . |ioo 

KELLEY. — Speeches, Addresses, and Letters on Industrial and 
Financial Questions : 
By Hon. William D. Kelley, M. C. 544 pages, 8vo. . #2.50 

KELLOGG.— A New Monetary System : 
The only means of Securing the respective Rights of Labor and 
Property, and of Protecting the Public from Financial Revulsions. 
By Edward Kellogg. i2mo. Paper cover, $1.00. Bound in 
cloth $1.25 

KEMLO.— Watch- Repairer's Hand-Book : 
Being a Complete Guide to the Young Beginner, in Taking Apart 
Putting Together, and Thoroughly Cleaning the English Lever and 
other Foreign Watches, and all American Watches. By F. K.EMLo t 
Practical Watchmaker. With Illustrations. 121110. . #1.25 



r.6 HENRY CAREY BAIRD & CO.'S CATALOGUE. 



KENTISH.— A Treatise on a Box of Instruments, 

And the Slide Rule ; with the Theory of Trigonometry and Loga 
rithms, including Practical Geometry, Surveying, Measuring of Tim. 
ber, Cask and Malt Gauging, Heights, and Distances. By Thoma* 
Kentish. In one volume. i2mo. .... $i.oo 

KERL.— The Assayer's Manual : 

An Abridged Treatise on the Docimastic Examination of Ores, and 
Furnace and other Artificial Products. By Bruno Kerl, Professor 
in the Royal School of Mines. Translated from the German by 
William T. Brannt. Second American edition, edited with Ex- 
tensive Additions by F. Lynwood Garrison, Member of the 
American Institute of Mining Engineers, etc. Illustrated by 87 en- 
gravings. 8vo. (Scarce.; 
KICK.— Flour Manufacture . 
A Treatise on Milling Science and Practice. By Frederick Kick 
Imperial Regierungsrath. Professor of Mechanical Technology in tht 
imperial German Polytechnic Institute, Prague. Translated from 
the second enlarged and revised edition with supplement by H. H. 
P. Powles, Assoc. Memb. Institution of Civil Engineers. Illustrated 
with 28 Plates, and 167 Wood-cuts. 367 pages. 8vo. . $10.00 
KINGZETT.— The History, Products, and Processes of the 
Alkali Trade : 
Including the most Recent Improvements. By Charles Thomas 
Ktngzett. Consulting; Chemist. With 23 illustrations. 8vo. $2. SO 
KIRK. — The Cupola Furnace: 

A Practical Treatise on the Construction and Management of Foundryv 
Cupolas. By Edward Kirk, Practical Moulder and Melter, Con- 
sulting Expert in Melting. Author of " The Founding of Metals." 
Illustrated by 78 engravings. 8vo. 379 pages. . . $3-5° 
LANDRIN.— A Treatise on Steel: 

Comprising its Theory, Metallurgy, Properties, Practical Working, 
and Use. By M. H. C. Landrin, Jr. From the French, by A. A. 

Fesquet. i2mo $2.50 

LANGBEIN.— A Complete Treatise on the Electro-Deposi. 
tion of Metals : 
Comprising Electro-Plating and Galvanoplastic Operations, the De- 
position of Metals by the Contact and Immersion Processes, the Color- 
ing of Metals, the Methods of Grinding and Polishing, as well as 
Descriptions of the Electric Elements, Dynamo-Electric Machines, 
Thermo-Piles and of the Materials and Processes used in Every De- 
partment of the Art. From the German of Dr. George Langbein, 
with additions by Wm. T. Brannt. Fourth Edition, thoroughly revised 
and much enlarged. 150 Engravings. 550 pages. 8vo. 1902. $4.00 

LARDNER.— The Steam-Engine: 

For the Use of Beginners. Illustrated. i2mo. ... 60 

LEHNER.- The Manufacture of Ink: 

Comprising the Raw Materials, and the Preparation df Waiting, 
Copying and- Hektograph Inks, Safety Inks, Ink Extracts and Pow- 
ders, etc. Translated from the German of Sigmund Lehner, with 
additions by William T. Brannt. Illustrated. i2mo. #2.00 



HENRY CAREY BAIRD & CO.'S- CATALOGUE 17 



LARKIN. — The Practical Brass and Iron Founder's Guide ; 

A Concise Treatise on Brass Founding, Moulding, the Metals and 
their Alloys, etc.; to which are added Recent Improvements in the 
Manufacture of Iron, Steel by the Bessemer Process, etc., etc. S} 
JAMES Larkin, late Conductor of the Brass Foundry Department it 
Reany, Neafie & Co.'s Penn Works, Philadelphia. New edition, 
revised, with extensive additions. 414 pages. 121110. . $2.50 

LEROUX.— A Practical Treatise on the Manufacture o* 
Worsteds and Carded Yarns : 
Comprising Practical Mechanics, with Rules and Calculations applied 
to Spinning; Sorting, Cleaning, and Scouring Wools; the English 
and French Methods of Combing,' Drawing, and Spinning Worsteds, 
and Manufacturing Carded Yarns. Translated from the French of 
Charles Leroux, Mechanical Engineer and Superintendent of a 
Spinning-Mill, by Horatio Paine, M. D., and A. A. Fesquet, 
Chemist and Engineer. Illustrated by twelve large Plates. To which 
is added an Appendix, containing Extracts from the Reports of the 
International Jury, and of the Artisans selected by the Committee 
appointed by the Council of the Society of Arts, London, on Wooler 
and Worsted Machinery and Fabrics, as exhibited in the Paris Uni- 
versal Exposition, 1867. 8vo. $5-oc 

LEFFEL. — The Construction of Mill-Dams : 
Comprising also the Building of Race and Reservoir Embankments 
and Head-Gates, the Measurement of Streams, Gauging of Water 
Supply, etc. By James Leffel & Co. Illustrated by 58 engravings. 
8vo. #2.50 

LESLIE.— Complete Cookery: 
Directions for Cookery in its Various Branches. By Miss Leslie. 
Sixtieth thousand. Thoroughly revised, with the addition of New 
Receipts. i2mo. ........ $1-5° 

LE VAN. — The Steam Engine and the Indicator: 

Their Origin and Progressive Development; including the Most 
Recent Examples of Steam and Gas Motors, together with the Indi- 
cator, its Principles, its Utility, and its Application. By William 
Barnet .Le Van. Illustrated by 205 Engravings, chiefly of Indi- 
cator-Cards. 469 pp. 8vo. ...... $4.00 

LIEBER.— Assayer's Guide : 
Or, Practical Directions to Assayers, Miners, and Smelters, for the 
Tests and Assays, by Heat and by Wet Processes, for the Ores of all 
the principal Metals, of Gold and Silver Coins and Alloys, and of 
Coal, etc. By Oscar M. Lieber. Revised. 283 pp. 121110. #1.50^ 

kockwood's Dictionary of Terms : 

Used in the Practice of Mechanical Engineering, embracing those 
Current in the Drawing Office, Pattern Shop, Foundry, Fitting, Turn- 
ing, Smith's and Boiler Shops, etc., etc., comprising upwards of Six 
Thousand Definitions. Edited by a Foreman Pattern Maker, author 
of " Pattern Making." 417 pp. l2mo. , < . #3-OQ 



18 HENRY CAREY BAIRD & CO.'S CATALOGUE. 

LUKIN.— The Lathe and Its Uses : 

Or Instruction in the Art of Turning Wood and Metal. Including 
a Description of the Most Modern Appliances for the Ornamentation 
of Plane and Curved Surfaces, an Entirely Novel Form of Lathe 
for Eccentric and Rose-Engine Turning; A Lathe and Planing 
Machine Combined; and Other Valuable Matter Relating to the 
Art. Illustrated by 462 engravings. Seventh edition. 315 pages. 
8vo. #4.25 

MAIN and BROWN. — Questions on Subjects Connected witb 
the Marine Steam-Engine : 

And Examination Papers.; with Hints for their Solution. B> 
Thomas J. Main, Professor of Mathematics, Royal ""tfaval College, 
and Thomas Brown, Chief Engineer, R. N. i2mo., cloth . $1.00 

MAIN and BROWN. — The Indicator and Dynamometer: 
With their Practical Applications to the Steam-Engine. By Thomas 
J. Main, M. A. F. R., Ass't S. Professor Royal Naval College, 
Portsmouth, and Thomas Brown, Assoc. Inst. C. E., Chief Engineer 
R. N., attached to the R. N. College. Illustrated. 8vo. . 

MAIN and BROWN.— The Marine Steam-Engine. 
By Thomas J. Main, F. R. Ass't S. Mathematical Professor at the 
Royal Naval* College, Portsmouth, and Thomas Brown, Assoc. 
Inst. C. E., Chief Engineer R. N. Attached to the Royal Naval 
College. With numerous illustrations. 8vo. 

MAKINS.— A Manual of Metallurgy: 

By George Hogarth Makins. 100 engravings. Second edition 
rewritten and much enlarged. i2mo., 592 pages . . $3-O0 

MARTIN.— Screw-Cutting Tables, for the Use Jf Mechanic*) 

Engineers : 
Showing the Proper Arrangement of iVheels for Cutting the Threads 
of Screws of any Required Pitch; with a Table for Making the Uni 
versal Gas-Pipe Thread and Taps. By W. A. Martin, Engineer. 
8vo. ' . .50 

MICHELL.— Mine Drainage: 
Being a Complete and Practical Treatise on Direct-Acting Under 
ground Steam Pumping Machinery. With a Description of a largt 
number of the best known Engines, their General Utility and ihe 
Special Sphere of their Action, the Mode of their Application, and 
their Merits compared with other Pumping Machinery. By STEPHEH 
MlCHELL. Illustrated by 247 engravings. 8vo., 369 pages. $12 50 

MOLESWORTH.— Pocket-Book of Useful Formulae and 
Memoranda for Civil and Mechanical Engineers. 
By Guilford L. Molesworth, Member of the Institution of Civil 
Engineers, Chief Resident Engineer of the Ceylon Railway. Full- 
bound in Pocket-book form #1.00 



HENRY CAREY BAIRD & CO.'S CATALOGUE. 19 

WOORE. — The Universal Assistant and the Complete Me 
chanic : 

Containing over one million Industrial Facts, Calculations, Receipts, 
Processes, Trades Secrets, Rules, Business Forms, Legal Items, Etc., 
in every occupation, from the Household to the Manufactory. B5 
R. Moore. Illustrated by 500 Engravings. i2mo. . $2.5(7 

MORRIS. — Easy Rules for the Measurement of Earthworks : 
By means of the Prismoidal Formula. Illustrated with Numerous 
Wood-Cuts, Problems, and Examples, and concluded by an Exten- 
sive Table for finding the Solidity in cubic yards from Mean Areas, 
The whole being adapted for convenient use by Engineers, Surveyors 
Contractors, and others needing Correct Measurements of Earthwork. 
By Elwood Morris, C. E. 8vo #1.50 

MAUCHLINE.— The Mine Foreman's Hand-Book 

Of Practical and Theoretical Information on the Opening, Venti- 
lating, and Working of Collieries. Questions and Answers on Prac- 
tical and Theoretical Coal Mining. Designed to Assist Students and 
Others in Passing Examinations for Mine Foremanships. By 
Robert Mauchline, Ex-Inspector of Mines. A New, Revised and 
Enlarged Edition. Illustrated by 114 engravings. 8vo. 337 
pages .......... $3-75 

NAPIER. — A System of Chemistry Applied to Dyeing. 
By James Napier, F. C. S. A New and Thoroughly Revised Edi* 
tion. Completely brought up to the present state of the Science, 
including the Chemistry of Coal Tar Colors, by A. A. Fesqtjet, 
Chemist and Engineer. With an Appendix on Dyeing and Calico 
Printing, as -shown at the Universal Exposition, Paris, 1867. Illus- 
trated. 8vo. 422 pages $3.00 

NEVILLE.— Hydraulic Tables, Coefficients, and Formulae, foi 
finding the Discharge of Water from Orifices, Notches f 
Weirs, Pipes, and Rivers : 
Third Edition, with Additions, consisting of New Formulae for the 
Discharge from Tidal and Flood Sluices and Siphons; general infor- 
mation on Rainfall, Catchment-Basins, Drainage, Sewerage, Water 
Supply for Towns and Mill Power. By Tohn Neville, C. E. M R. 
I. A. ; Fellow of the Royal Geological Society of Ireland. Thicfc 
I2mo I5.5C 

NEWBERY- Gleanings from Ornamental Art of every 
style : 
Drawn from Examples in the British, South Kensington, Indian, 
Crystal Palace, and other Museums, the Exhibitions of 185 1 and 
1862, and the best English and Foreign works. In a series of ioq 
exquisitely drawn Plates, containing many hundred examples. Btf 
Robert Newbery. 4to. ...... (Scarce. J 

NICHOLLS. —The Theoretical and Practical Boiler-Maker *nd 
Engineer's Reference Book: 
Containing a variety of Useful Information for Employers of Labor 
Foremen a'\d Working Boiler-Makers. Iroa, Copper, and Tinsmiths 



2 o HENRY CAREY BAIRD & CO.'S CATALOGUE. 

.Draughtsmen, Engineers, the General Steam-using Public, and for the 
Use of Science Schools and Classes. By Samuel Nicholls. Illus 
trated by sixteen plaies, i2mo. ..... $2.$c 

NICHOLSON.— A Manual of the Art of Bookbinding : 

Containing full instructions in the different Branches of Forwarding, 
Gilding, and Finishing. Also, the Art of Marbling Book-edges and 
Paper. By James B. Nicholson. Illustrated. i2mo., cloth $2.25 

NICOLLS.— The Railway Builder: 
A Hand-Book for Estimating the Probable Cost of American Rail- 
way Construction and Equipment. By WILLIAM J. NlCOLLS, Civil 
Engineer. Illustrated, full bound, pocket-book form . $2.00 

NORMANDY.— The Commercial Handbook of Chemical An- 
alysis : 
Or Practical Instructions for the Determination of the Intrinsic 01 
Commercial Value of Substances used in Manufactures, in Trades, 
and in the Arts. By A. Normandy. New Edition, Enlarged, and 
to a great extent rewritten. By Henry M. Noad, Ph.D., F.R.S., 
thick i2mo $5-oc 

N ORRIS. — A Handbook for Locomotive Engineers and Ma- 
chinists : 
Comprising the Proportions and Calculations for Constructing Loco- 
motives; Manner of Setting Valves; Tables cf Squares, Cubes, Areas, 
etc., etc. By Septimus Norris, M. E. New edition. Illustrated, 
I2mo $i.$q 

NYSTROM. — A New Treatise on Elements of Mechanics : 
Establishing Strict Precision in the Meaning of Dynamical Terms s 
accompanied with an Appendix on Duodenal Arithmetic and Me 
trology. By John W. Nystrom, C. E. Illustrated. 8vo. #3. cm 

NYSTROM. — On Technological Education and the Construc- 
tion of Ships and Screw Propellers : 
For Naval and Marine Engineers. By John W. Nystrom, lat* 
Acting Chief Engineer, U. S. N. Second edition, revised, with addi 
tional matter. Illustrated by seven engravings. i2mo. . $l.2< 

O'NEILL. — A Dictionary of Dyeing and Calico Printing: 
Containing a brief account of all the Substances and Processes it 
use in the Art of Dyeing and Printing Textile Fabrics ; with Practical 
Receipts and Scientific Information. By Charles O'Neill, Analy- 
tical Chemist. To which is added an Essay on Coal Tar Colors and 
their application to Dyeing and Calico Printing. By A. A. Fesquet, 
Chemist and Engineer. With an appendix on Dyeing and Calico 
Printing, as shown at the Universal Exposition, Paris, 1867- 8vo., 
491 pages $3.00 

ORTON. — Underground Treasures'. 
How and Where to Find Them. A Key for the Ready Determination 
of ail the Useful Minerals within the United States. By James 
OlTON, A.M., Late Professor of Natural History in Vassar College, 
N. Y.; author of the "Andes and the Amazon," etc. A New Edi- 
tion, with An Appendix on Ore Deposits and Testing Minerals (1901). 
Illustrated $1.50 



HENRY CAREY BAIRD & CO.'S CATALOGUE. 21 

OSBORN.— The Prospector's Field Book and Guide. 

In the Search For and the Easy Determination of Ores and Other 
Useful Minerals. By Prof. H. S. Osborn, LL. D. Illustrated by 58 
Engravings. i2rno. Fifth Edition. Revised and Enlarged 

O901) |i. 5 o 

OSBORN— A Practical Manual of Minerals, Mines and Min- 
ing : 
Comprising the Physical Properties, Geologic Positions, Local Occur- 
rence and Associations of the Useful Minerals; their Methods of 
Chemical Analysis and Assay ; together with Various Systems of Ex- 
cavating and 'limbering, Brick and Masonry Work, during Driving, 
Lining, Bracing and other Operations, etc. By Prof. H. S. OSBORN, 
LL. D., Author of •' The Prospector's Field-Book and Guide." 171 
engravings. Second Edition, revised. 8vo. . . . $4.50 

OVERMAN.— Th« Manufacture of Steel : 
Containing the Practice and Principles of Working and Making Steel. 
A Handbook for Blacksmiths and Workers in Steel and Iron, Wagon 
Makers, Die Sinkers, Cutlers, and Manufacturers of Files and Hard- 
ware, of Sleel and Iron, and for Men of Science and Art. By 
Frederick Overman, Mining Engineer, Author of the " Manu- 
facture of Lon," etc. A new, enlarged, and revised Edition. By 
A. A. FesqLfST, Chemist and Engineer. i2mo. . . $1.50 

OVERMAN. —The Moulder's and Founder's Pocket Guide : 
A Treatise or. Moulding and Founding in Green-sand, Dry -sand, Loam, 
and Cement; the Moulding of Machine Frames, Mill-gear, Hollow- 
ware, Ornaments, Trinkets, Bells, and Statues; Description of Moulds 
for Iron, Bronze, Brass, and other Metals; Plaster of Paris, Sulphur, 
Wax, etc. ; the Construction of Melting Furnaces, the Melting and 
Founding of Metals ; the Composition of Alloys and their Nature, 
etc., etc. By Frederick Overman, M. E. A new Edition, to 
which is added a Supplement on Statuary and Ornamental Moulding, 
Ordnance, Malleable Iron Castings, etc. By A. A. Fesquet, Chem- 
ist and Engineer. Illustrated by 44 engravings. l2mo. . $2.0t. 
PAINTER, GILDER. AND VARNISHER'S COMPANION. 
Comprising the Manufacture and Test of Pigments, the Arts of Paint- 
ing, Graining, Marbling, Staining, Sign- writing, Varnishing, Glass- 
staining, and Gilding on Glass; together with Coach Painting and 
Varnishing, and the Principles of the Harmony and Contrast of 
Colors. Twenty-seventh Edition. Revised, Enlarged, and in great 
part Rewritten. By William T. Brannt, Editor of " Varnishes, 
Lacquers, Printing Inks and Sealing Waxes." Illustrated. 395 pp. 

121110. . . . , $1 .50 

PALLETT.- The Miller's, Millwright's, and Engineer's Guide. 
By Henry Pallett. Illustrated. i2mo. . . . $2.00 



22 HENRY CAREY BAIRD & CO.'S CATALOGUE. 

PERCY.— The Manufacture of Russian Sheet-Iron. 

By John Percy, M. D., F. R. S. Paper. ... 25 cts. 
PERKINS.— Gas and Ventilation: 

Practical Treatise on Gas and Ventilation. Illustrated. i2mo. $1.25 

PERKINS AND STOWE.-A New Guide to the Sheet-iron 
and Boiler Plate Roller : 
Containing a Series of Tables showing the Weight of Slabs and Piles 
to Produce Boiler Plates, and of the Weight of Piles and the Sizes of 
Bars to produce Sheet-iron ; the Thickness of the Bar Gauge 
in decimals ; the Weight per foot, and the Thickness on the Bar or 
Wire Gauge of the fractional parts of an inch; the Weight per 
sheet, and the Thickness on the Wire Gauge of Sheet-iron of various 
dimensions to weigh 1 12 lbs. per bundle; and the conversion of 
Short Weight into Long Weight, and Long Weight into Short. 

#1.50 

POSSELT. — Recent Improvements in Textile Machinery Re- 
lating to Weaving : 
Giving the Most Modern Points on the Construction of all Kinds 
of Looms, Warpers, Beamers, Slashers, Winders, Spoolers, Reeds, 
Temples, Shuttles, Bobbins, Heddles, Heddle Frames, Pickers, 
Jacquards, Card Stampers, etc., etc. 600 illus. . . $3-00 

POSSELT. — Technology of Textile Design: 

The Most Complete Treatise on the Construction and Application 
of Weaves for all Textile Fabrics and the Analysis of Cloth. By E. 
A. Posselt. 1,500 illustrations. 4to. .... $5-00 

POSSELT. — Textile Calculations: 

A Guide to Calculations Relating to the Manufacture of all Kinds 
of Yarns and Fabrics, the Analysis of Cloth, Speed, Power and Belt 
Calculations. By E. A. POSSELT. Illustrated. 410. . $2.00 

REGNAULT.— Elements of Chemistry: 

By M. V. Regnault. Translated from the French by T. Forrest 
Betton, M. D., and edited, with Notes, by James C. Booth, Melter 
and Refiner U. S. Mint, and William L. Faber, Metallurgist and 
Mining Engineer. Illustrated by nearly 700 wood-engravings. Com- 
prising nearly 1,500 pages. In two volumes, 8vo., cloth . $6.00 

RICHARDS.— Aluminium : 

Its History, Occurrence, Properties, Metallurgy and Applications, 
including its Alloys. By Joseph W. Richards, A. C, Chemist and 
Practical Metallurgist, Member of the Deutsche Chemische Gesell- 
schaft. Illusr. Third edition, enlarged and revised (1895) . $6.00 

RIFFAULT, VERGNAUD, and TOUSSAINT.— A Practical 
Treatise on the Manufacture of Colors for Painting : 
Comprising the Origin, Definition, and Classification of Colors; the 
Treatment of the Raw Materials ; the best Formula? and the Newest 
Processes for the Preparation of every description of Pigment, and 
the Necessary Apparatus and Directions for its Use; Dryers; the 
Testing. Application, and Qualities of Paints, etc., etc. By MM. 
Riffault, Vergnaud, and Toussaint. Revised and Edited by M. 



HENRY CAREY BAIRD & CO.'S CATALOGUE. 23 

F. Malepeyre. Translated from the French, by A. A. FesquxK) 
Chemist and Engineer. Illustrated by Eighty engravings. In one 
vol., 8vo., 659 pages $5.00 

ROPER. — A Catechism of High-Pressure, or Non-Condensing 
Steam -Engines : 
Including the Modelling, Constructing, and Management of Steam- 
Engines and Steam Boilers. With valuable illustrations. By Ste- 
phen Roper, Engineer. Sixteenth edition, revised and enlarged. 
1 8mo., tucks, gilt edge ....... $2.oc 

I OPER.— Engineer's Handy-Book: 
Containing a full Explanation of the Steam-Engine Indicator, and its 
Use and Advantages to Engineers and Steam Users. With Formulae 
for Estimating the Power of all Classes of Steam-Engines ; also. 
Facts, Figures, Questions, and Tables for Engineers who wish to 
qualify themselves for the United States Navy, the Revenue Service, 
the Mercantile Marine, or to take charge of the Better Class of Sta- 
tionary Steam-Engines. Tenth edition. i6mo., 690 pages, tucks, 
gilt edge #3.50 

ROPER. — Hand-Book of Land and Marine Engines : 
Including the Modelling, Construction, Running, and Management 
of Land and Marine Engines and Boilers. With illustrations, riy 
Stephen Roper, Engineer. Sixth edition. i2mo., ticks, gilt edge. 

#3-5c 
ROPER. — Hand-Book of the Locomotive : 

Including the Construction of Engines and Boilers, and the Construc- 
tion, Management, and Running of Locomotives. By Stephen 
Roper. Eleventh edition. i8mo., tucks, gilt edge . $2.5G 

ROPER.— Hand-Book of Modern Steam Fi-e-Engines. 

With illustrations. By Stephen Roper, Engineer. Fourth edition, 
i2mo., tucks, gilt edge . . . ' . . . . $3-S c 
ROPER. — Questions and Answers for Engineers. 
This little book contains all the Questions that Engineers will be 
asked when undergoing an Examination for the purpose of procuring 
Licenses, and they are so plain that any Engineer or Fireman of or 
dinary intelligence may commit them to memory in a short time. By 
Stephen Roper, Engineer. Third edition . . . $2.00 
ROPER.— Use and Abuse of the Steam Boiler. 

By Stephen Roper, Engineer. Eighth edition, with lustrations. 

i8mo., tucks, gilt edge $2.0C 

ROSE.— The Complete Practical Machinist : 

Embracing Lathe Work, Vise Work, Drills and Drilling, Taps and 
Dies, Hardening and Tempering, the Making and Use of Tools 
Tool Grinding, Marking out Work, Machine Tools, etc. By Joshua 
Rose. 39s Engravings. Nineteenth Edition, greatly Enlarged with 
New and Valuable Matter. i2mo., 504 pages. . . $2.50 

ROSE.— Mechanical Drawing Self-Taught : 

Comprising Instructions in the Selection and Preparation of Drawing 
Instruments, Elementary Instruction in Practical Mechanical Draw- 



24 HENRY CAREY BAIRD & CO.'S CATALOGUE. 

ing, together with Examples in Simple Geometry and Elementary 
Mechanism, including Screw Threads, Gear Wheels, Mechanical 
Motions, Engines and Boilers. By Joshua Rose, M. E. Illustrated 
by 330 engravings. 8vo ,313 pages" .... $4.00 

ROSE.— The Slide- Valve Practically Explained: 

Embracing simple and complete Practical Demonstrations of th 
operation of each element in a Slide-valve Movement, and illustrat- 
ing the effects of Variations in their Proportions by examples care- 
fully selected from the most recent and successful practice. By 
Joshua Rose, M. E. Illustrated by 35 engravings . $t.co 

ROSS. — The Blowpipe in Chemistry, Mineralogy and Geology: 

Containing all Known Methods of Anhydrous Analysis, many Work- 
ing Examples, and Instructions for Making Apparatus. By LiEUT.- 
Colonel W. A. Ross, R. A., F. G. S. With 120 Illustrations. 

I2mo $2.00 

SHAW.— Civil Architecture : 

Being a Complete Theoretical and Practical System of Building, con- 
taining the Fundamental Principles of the Art. By Edward Shaw, 
Architect. To which is added a Treatise on Gothic Architecture, etc. 
By Thomas W. Silloway and George M. Harding, Architects. 
The whole illustrated by 102 quarto plates finely engraved on copper. 
Eleventh edition. 4to #6.00 

SHUNK. — A Practical Treatise on Railway Curves and Loca- 
tion, for Young Engineers. 

By W. F. Shunk, C. E. 121110. Full bound pocket-book form $2.00 

SLATER.— The Manual of Colors and Dye Wares. 

By J. W. Slater. i2mo $3-oo 

SLOAN. — American Houses : 

A variety of Original Designs for Rural Buildings. Illustrated by 
26 colored engravings, with descriptive references. By Samuel 
Sloan, Architect. 8vo. .75 

SLOAN. — Homestead Architecture: 

Containing Forty Designs for Villas, Cottages, and Farm-houses, with 
Essays on Style, Construction, Landscape Gardening, Furniture, etc., 
etc. JUustrated by upwards of 200 engravings. By SAMUEL SLOAN, 
Architect. 8vo. ... . .... $2 50 

SLOANE.-Ho.re Experiments m Science. 

By T. O'Conor Slc\ne, E.M., A.M., Ph.D. Illustrated by 91 
engravings. i2mo. ....... $1.00 

SMEATON.— Builder's Pockt^Companion : 

Containing the Elements of Building, Surveying, and Architecture; 
with Practical Rules and Instructions connected with the subject. 
By A. C. Smeaton, Civil Engineer, etc. i2mo. 

SMITH.— A Manual of Political Economy. 

By E. Peshine Smith. A New Edition, to which is added a full 
Index. i2mo , $1 -25 



HENRY CAREY BAIRD & CO.'S CATALOGUE. 25 

SMITH.— Parks and Pleasure-Grounds : 

Or Practical Notes on Country Residences, Villas, Public Parks, and 
Gardens. By Charles H. J. Smith, Landscape Gardener and 
Garden Architect, etc., etc. 121110. .... $2.og 

SMITH.— The Dyer's Instructor: 

Comprising Practical Instructions in the Art of Dyeing Silk, Cotton, 
Wool, and Worsted, and Woolen Goods ; containing nearly 800 
Receipts. To which is added a Treatise on the Art of Padding; and) 
the Printing of Silk Warps, Skeins, and Handkerchiefs, and thei 
various Mordants and Colors for the different styles of such work/ 
By David Smith, Pattern Dyer. i2mo. . . . $1.50; 

SMYTH. — A Rudimentary Treatise on Coal and Coal-Mining. 
By Warrington W. Smyth, M. A., F. R. G., President R. G. S. 
of Cornwall. Fifth edition, revised and corrected. With numer- 
ous illustrations. 121110. ...... $*«7$ 

SNIVELY. — Tables for Systematic Qualitative Chemical Anal, 
ysis. 
By John H. Snively, Phr. D. 8vo. .... $1.00 

SNIVELY. — The Elements of Systematic Qualitative vhemical 
Analysis : 
A Hand-book for Beginners. By John H. Snively, Phr. D. i6mo. 

$2.oa 
STOKES. — The Cabinet Maker and Upholsterer's Companion-. 
Comprising the Art of Drawing, as applicable to Cabinet Work; 
Veneering, Inlaying, and Buhl-Work; the Art of Dyeing and Stain- 
ing Wood, Ivory, Bone, Tortoise-Shell, etc. Directions for Lacker- 
ing, Japanning, and Varnishing; to make French Polish, Glues. 
Cements, and Compos'- ns; with numerous Receipts, useful to work 
men generally. Br Stokes. Illustrated. A New Edition, with 
an Appendix upor .ench Polishing, Staining, Imitating, Varnishing, 

etc., etc. i2mo $1.25 

STRENGTH AND OTHER PROPERTIES OF METALS: 
Reports of Experiments on the Strength and other Properties of 
Metals for Cannon. Wiih a Description of the Machines for Testing 
Metals, and of the Classification of Cannon in service. By Officer* 
of the Ordnance Department, U. S. Army. By authority of the Secre- 
taryof War. Illustrated by 25 large steel plates. Quarto . $5.00 
SULLIVAN. — Protection to Native Industry. 

By Sir Edward Sullivan, Baronet, author of "Ten Chapters on 

Social Reforms." 8vo , $1.00 

SHERRATT.— The Elements of Hand-Railing : 

Simplified and Explained in Concise Problems that are Easily Under- 
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?K HENRY CAREY BAIRt? & CO.'S CATALOGUE. 

SYME. — Outlines of an Industrial Science. 

By David Syme. i2mo. . ... #2.oc 

TABLES SHOWING THE WEIGHT OF ROUND, 
SQUARE, AND FLAT BAR IRON, STEEL, ETC., 

By Measurement. Cloth ...... 63 

TAYLOR.— Statistics of Coal : 

Including Mineral Bituminous Substances employed in Arts and 
Manufactures ; with their Geographical, Geological, and Commercial 
Distribution and Amount of Production and Consumption on the 
American Continent. With Incidental Statistics of the Iron Manu- 
facture. By R. C. Taylor. Second edition, revised by S. S. Halde- 
man. Illustrated by five Maps and many wood engravings. 8vo., 
cloth $6.00 

TEMPLETON.— The Practical Examinator on Steam and the 

Steam -Engine: 

With Instructive References relative thereto, arranged for the Use of 

Engineers, Students, and others. By William Templeton, En. 

gineer. i2mo. . $1.00 

FHAUSING.— The Theory and Practice of the Preparation of 
Malt and the Fabrication of Beer: 
With especial reference to the Vienna Process of Brewing. Elab 
orated from personal experience by Julius E. Thausing, Professor 
at the School for Brewers, and at the Agricultural Institute, Modling, 
near Vienna. Translated from the German by William T Brannt, 
Thoroughly and elaborately edited, with much American matter, and 
according to the latest and most Scientific Practice, by A. Schwarz 
and Dr. A. H. Bauer. Illustrated by 140 Engravings. 8vo., 815 
pages .......... $10.00 

THOMPSON.— Political Economy. With Especial Reference 
to the Industrial History of Nations : 
By Robert E. Thompson, M. A., Professor of Social Science in the 
University of Pennsylvania. l2mo. . . . . $1.50 

THOMSON.— Freight Charges Calculator: 

By Andrew Thomson, Freight Agent. 24mo. * . $1.25 

TURNER'S (THE) COMPANION: 

Containing Instructions in Concentric, Elliptic, and Eccentric Turn, 
ing; also various Plates of Chucks, Tools, and Instruments; and 
Directions for using the Eccentric Cutter, Drill, Vertical Cutter, and 
Circular Rest; with Patterns and Instructions for working them, 
l2mo. $1.00 

TURNING : Specimens of Fancy Turning Executed on the 

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With Geometric, Oval, and Eccentric Chucks, and Elliptical Cutting 

Frame. By an Amateur. Illustrated by 30 exquisite Photographs. 

4*o $2.50 



HENRY CAREY BAIRD & CO.'S CATALOGUE. 27 

VAILE. — Galvanized-Iron Cornice-Worker's Manual: 

Containing Instructions in Laying out the Different Mitres, and 
Making Patterns for all kinds of Plain and Circular Work. Also* 
Tables of Weights, Areas and Circumferences of Circles, and other 
Matter calculated to Benefit the Trade. By Charles A. Vaile. 
Illustrated by twenty-one plates. 4to $5-O0 

VILLE.— On Artificial Manures : 
Their Chemical Selection and Scientific Application to Agriculture. 
A series of Lectures given at the Experimental Farm at Vincennes, 
during 1867 and 1874-75. By M. Georges Ville. Translated and 
Edited by William Crookes, F. R. S. Illustrated by thirty-one 
engravings. 8vo., 450 pages ...... $6.00 

VILLE.— The School of Chemical Manures : 
Or, Elementary Principles in the Use of Fertilizing Agents. From 
the French of M. Geo. Ville, by A. A. Fesquet, Chemist and En- 
gineer. With Illustrations. i2mo. .... $1.25 

VOGDES. — The Architect's and Builder's Pocket- Companion 
and Price-Book : 
Consisting of a Shoit but Comprehensive Epitome of Decimals, Duo- 
decimals, Geometry and Mensuration ; with Tables of United States 
Measures, Sizes, "Weights, Strengths, etc., of Iron, Wood, Stone, 
Brick, Cement and Concretes, Quantities of Materials in given Sizes 
and Dimensions of Wood, Brick and Stone; and full and complete 
Bills of Prices for Carpenter's Work and Painting ; also, Rules for 
Computing and Valuing Brick and Brick Work, Stone Work, Paint- 
ing, Plastering, with a Vocabulary of Technical Terms, etc. By 
Frank W. Vogdes, Architect, Indianapolis, Ind. Enlarged, revised, 
and corrected. In one volume, 368 pages, full-bound, pocket-book 

form, gilt edges $2.oc 

Cloth . . I.50 

VAN CLEVE.— The English and American Mechanic : 
Comprising a Collection of Over Three Thousand Receipts, Rules, 
and Tables, designed for the Use of every Mechanic and Manufac- 
turer. By B. Frank Van Cleve. Illustrated. 500 pp. i2mo. $2.00 

WAHNSCHAFFE.— A Guide to the Scientific Examination 
of Soils: 
Comprising Select Methods of Mechanical and Chemical Analysis 
and Physical Investigation. Translated from the German of Dr. F. 
Wahnschaffe. With additions by William T. Brannt. Illus- 
trated by 25 engravings. 121110. 177 pages . . . $1.50 

WALL. — Practical Graining : 

With Descriptions of Colors Employed and Tools Used. Illustrated 
by 47 Colored Plates, Representing the Various Woods Used 4; 
Interior Finishing. By William E. Wall. 8vo. (Scarce.) 

WALTON.— Coal-Mining Described and Illustrated: 
By Thomas H. Walton, Mining Engineer. Illustrated by 24 large 
and elaborate Plates, after Actual Workings and Apparatus, ,85.0c 



2S HENRY CAREY BAIRD & CO.'S CATALOGUE. 



?VARE.— The Sugar Beet. 
Including a History of the Beet Sugar Industry in Europe, Varieties 
of the Sugar Beet, Examination, Soils, Tillage, Seeds and Sowings 
Yield and Cost of Cultivation, Harvesting, Transportation, Conserva 
tion, Feeding Qualities of the Beet and of the Pulp, etc. By Lewi? 
S. Ware, C. E., M. E. Illustrated by ninety engravings. 8vo. 

WARN.— The Sheet-Metal Worker's Instructor: 

For Zinc, Sheet-Iron, Copper, and Tin-Plate Workers, etc. Contain- 
ing a selection of Geometrical Problems ; also, Practical and Simple 
Rules for Describing the various Patterns required in the different 
branches of the above Trades. By Reuben H. Warn, Practical 
Tin-Plate Worker. To which is added an Appendix, containing 
Instructions for Boiler-Making, Mensuration of Surfaces and Solids, 
Rules for Calculating the Weights of different Figures of Iron and 
Steel, Tables of the Weights of Iron, Steel, etc. Illustrated by thirty- 
two Plates and thirty-seven Wood Engravings. 8vo. . $3-00 

WARNER. — New Theorems, Tables, and Diagrams, for the 

Computation of Earth-work : 
Designed for the use of Engineers in Preliminary and Final Estimates 
of Students in Engineering, and of Contractors and other non-profes- 
sional Computers. In two parts, with an Appendix. Part I. A Prac- 
tical Treatise; Part II. A Theoretical Treatise, and the Appendix, 
Containing Notes to the Rules and Examples of Part I.; Explana- 
tions of the Construction of Scales, Tables, and Diagrams, and a 
Treatise upon Equivalent Square Bases and Equivalent Level Heights, 
By John Warner, A. M., Mining and Mechanical Engineer. Illus- 
trated by 14 Plates. 8vo. . . . . ' . . $3.00 

WILSON. — Carpentry and Joinery: 

By John Wilson, Lecturer on Building Construction, Carpentry and 
Joinery, etc., in the Manchester Technical School. Third Edition, 
with 65 full page plates, in flexible cover, oblong . . . .80 

WATSON. — A Manual of the Hand-Lathe : 

Comprising Concise Directions for Working Metals of all kinds, 
Ivory, Bone and Precious Woods; Dyeing, Coloring, and French 
Polishing; Inlaying by Veneers, and various methods practised to 
produce Elaborate work with Dispatch, and at Small Expense. By 
Egbert P. Watson, Author of " The Modern Practice of American 
Machinists and Engineers." Illustrated by 78 engravings. $1.50 

WATSON. — The Modern Practice of American Machinists and 
Engineers 

Including the Construction, Application, and Use of Drills, Lathe 
Tools, Cutters for Boring Cylinders, and Hollow-work generally, with 
the most Economical Speed for the same; the Results verified b> 
Actual Practice at the Lathe, the Vise, and on the Floor. Togethe< 



HENRY CAREY BAIRD & CO.'S CATALOGUE. 29 



with Workshop Management, Economy of Manufacture, the Steam 
Engine, Boilers, Gears, Belting, etc., etc. By Egbert P. Watson. 
Illustrated by eighty-six engravings. i2mo. . . . $2.50 

WATT.— The Art of Soap Making : 

A Practical Hand-Book of the Manufacture of Hard and Soft Soaps, 
Toilet Soaps, etc. Fifth Edition, Revised, to which is added an 
Appendix on Modern Candle Making. By Alexander Watt. 
111. 121110 $3.00 

WEATHERLY.- Treatise on the Art of Boiling Sugar, Crys- 
tallizing, Lozenge-making, Comfits, Gum Goods, 
And other processes for Confectionery, etc., in which are explained, 
in an easy and familiar manner, the various Methods of Manufactur- 
ing every Description of Raw and Refined Sugar Goods, as sold by 
Confectioners and others. l2mo. ..... $150 

WILL.— Tables of Qualitative Chemical Analysis : 

With an Introductory Chapter on the Course of Analysis. By Pro- 
fessor Heinrich Will, of Giessen, Germany. Third American, 
from the eleventh German edition. Edited by CHARLES F. Himes, 
Ph. D., Professor of Natural Science, Dickinson College, Carlisle, 
Pa. 8vo #1.50 

WILLIAMS.— On Heat and Steam : 

Embracing New Views of Vaporization, Condensation and Explo- 
sion. By Charles Wye Williams, A. I. C. E. Illustrated. 8vo. 

$2.50 

WILSON.— First Principles of Political Economy: 

With Reference to Statesmanship and the Progress of Civilization. 
By Professor W. D. WlLSON, of the Cornell University. A new and 
revised edition. i2mo. ....... $1-5° 

WILSON.— The Practical Tool-Maker and Designer: 

A Treatise upon the Designing of Tools and Fixtures for Machine 
Tools and Metal Working Machinery, Comprising Modern Examples 
of Machines with Fundamental Designs for Tools for the Actual Pro- 
duction of the work; Together with Special Reference to a Set of 
Tools for Machining the Various Parts of a Bicycle. Illustrated by 
189 engravings. 1898. ....... $2.50 

CONTENTS : Introductory. Chapter I. Modern Tool Room and Equipment. 
II. Files, Their Use and Abuse. III. Steel and Tempering. IV. Making Jigs. 
V. Milling Machine Fixtures. VI. Tools and Fixtures for Screw Machines. VII. 
Broaching. VIII. Punches and Dies for Cutting and Drop Press. IX. Tools for 
Hollow- Ware. X. Embossing: Metal, Coin, and Stamped Sheet-Metal Orna- 
ments. XI. Drop Forging. XII. Solid Drawn Shells or Ferrules; Cupping or 
Cutting, and Drawing ; Breaking Down Shells. XIII. Annealing, Pickling and 
Cleaning. XIV. Tools for Draw Bench. XV. Cutting and Assembling Pieces 
by Means of Ratchet Dial Plates at One Operation. XVI. The Header. XVII. 
Tools for Fox Lathe. XVIII. Suggestions for a Set of Tools for Machining the 
Various Parts of a Bicycle. XIX. The Plater's Dynamo. XX. Conclusion — 
With a Few Random Ideas. Appendix. Index. 

WOODS. — Compound Locomotives : 

By Arthur Tannatt Woods. Second edition, revised and enlarged 
by David Leonard Barnes, A. M., C. E. 8vo. 330 pp. #300 



30 HENRY CAREY BAIRD & CO.'S CATALOGUE. 

WOHLER.-A Hand-Bookof Mineral Analysis: 

By F. WoHLER, Professor of Chemistry in the University of Gottin- 
gen. Edited by Henry B. Nason, Professor of Chemistry in the 
Renssalaer Polytechnic Institute, Troy, New York. Illustrated. 
i2mo. 

WORSSAM.— On Mechanical Saws: 

From the Transactions of the Society of Engineers. 1869. By S. W. 
Worssam, Jr. Illustrated by eighteen large plates. 8vo. $1.50 



RECENT ADDITIONS. 

BRANNT. — Varnishes, Lacquers, Printing Inks and Sealing- 1 
Waxes : 

Their Raw Materials and their Manufacture, to which is added the 
Art of Varnishing and Lacquering, including the Preparation of Put- 
ties and of Stains for Wood, Ivory, Bone, Horn, and Leather. By 
William T. Brannt. Illustrated by 39 Engravings, 338 pages. 
i2mo. .......... $3.00 

BRANNT — The Practical Scourer and Garment Dyer: 

Comprising Dry or Chemical Cleaning ; the Art of Removing Stains ; 
Fine Washing; Bleaching and Dyeing of Straw Hats, Gloves, and 
Feathers of all kinds; Dyeing of Worn Clothes of all fabrics, in- 
cluding Mixed Goods, by One Dip; and the Manufacture of Soaps 
and Fluids for Cleansing Purposes. Edited by William T. Brannt, 
Editor of "The Techno-Chemical Receipt Book." Illustrated. 
203 pages. i2mo. $2.00 

BRANNT.— Petroleum . 

its History, Origin, Occurrence, Production, Physical and Chemical 
Constitution, Technology, Examination and Uses; Together with 
the Occurrence and Uses of Natural Gas. Edited chiefly from the 
German of Prof. Hans Hoefer and Dr. Alexander Veith, by Wm. 
T. Brannt. Illustrated by 3 Plates and 284 Engravings. 743 pp. 
8vo. I7.50 

BRANNT. — A Practical Treatise on the Manufacture of Vine- 
gar and Acetates, Cider, and Fruit-Wines : 
Preservation of Fruits and Vegetables by Canning and Evaporation; 
Preparation of Fruit-Butters, Jellies, Marmalades, Catchups, Pickles, 
Mustards, etc. Edited from various sources. By William T. 
Brannt. Illustrated by 79 Engravings. 479 pp. 8vo. $6.00 

BRANNT.— The Metal Worker's Handy-Book of Receipts 
and Processes : 

Being a Collection of Clemical Formulas and Practical Manipula- 
tions for the working of all Metals ; including the Decoration and 
Beautifying of Articles Manufactured therefrom, as well as their 
Preservation. Edited from various sources. By Willi AM T. 
Brannt. Illustrated. i2mo. $2.50 



HEN^Y CAREY BAIRD & CO.'S CATALOGUE. $l 



iDEITE.— A Practical Treatise on the Manufacture cf Per- 
iurnery; 
Comprising directions for making all kinds of Perfumes, Sachet 
Powders, Fumigating Materials, Dentifrices, Cosmetics, etc., with a 
full account of the Volatile Oils, Balsams, Resins, and ether Natural 
and Artificial Perfume-substances, including the Manufacture of 
PYuit Ethers, and tests of their purity. By Dr. C. Deite, assisted 
by L. Borchert, F. Etchbaum, E. Kugler, H. Toeffner, and 
other experts. From the German, by Wm. T. Brannt. 28 Engrav- 
ings. 358 pages. 8vo. $3.00 

EDWARDS. — American Marine Engineer, Theoretical and 
Practical : 

With Examples of the latest and most approved American Practice. 
By Emory Edwards. 85 illustrations. i2mo. . . $2.50 

EDWARDS. — goo Examination Questions and Answers: 

For Engineers and Firemen (Land and Marine) who desire to ob- 
tain a United States Government or State License. Pocket-book 
form, gilt edge . . . . . . . . . $1.50 

KIRK.— The Cupola Furnace: 

A Practical Treatise on the Construction and Management of Foun- 
dry Cupolas. By Edward Kirk, Practical Moulder and Melter, 
author of "The Founding of Metals." Illustrated by 80 Engravings. 
8vo. (1899) $3.50 

POSSELT.— The Jacquard Machine Analysed and Explained: 
With an Appendix on the Preparation of Jacquard Cards, and 
Practical Hints to Learners of Jacquard Designing. By E. A. 
Posselt. With 230 illustrations and numerous diagrams. 127 pp. 
4to #3.00 

POSSELT.— The Structure of Fibres, Yarns and Fabrics: 

Being a Practical Treatise for the Use of all Persons Employed in 
the Manufacture of Textile Fabrics, containing a Description of the 
Growth and Manipulation of Cotton, Wool, Worsted, Silk Flax, 
Jute, Ramie, China Grass and Hemp, and Dealing with all Manu- 
facturers' Calculations for Every Class of Material, also Giving 
Minute Details for the Structure of all kinds of Textile Fabrics, and 
an Appendix of Arithmetic, specially adapted for Textile Purposes. 
By E. A. Posselt. Over 400 Illustrations, quarto. . $5.00 

RICH.— Artistic Horse-Shoeing: 

A Practical and Scientific Treatise, giving Improved Methods of 
Shoeing, with Special Directions for Shaping Shoes to Cure Different 
Diseases of the Foot, and for the Correction of Faulty Action in 
Trotters. By George E. Rich. 62 Illustrations. 153 pages, 
lamo. gi.oo 



32 HENRY CAREY BAIRD & CO.'S CATALOGUE. 

RICHARDSON.— Practical Blacksmithing : 

A Collection of Articles Contributed at Different Times by Skilled 
Workmen to the columns of " The Blacksmith and Wheelwright," 
and Covering nearly the Whole Range of Blacksmithing, from the 
Simplest Job of Work to some of the Most Complex Forgings. 
Compiled and Edited by M. T. Richardson. 

Vol.1. 210 Illustrations. 224 pages. i2mo. . . $1.00 

Vol. II. 230 Illustrations. 262 pages. i2mo. . . $1.00 
Vol. III. 390 Illustrations. 307 pages. i2mo. . , $1.00 
Vol. IV. 226 Illustrations. 276 pages. l2mo. , . $1.00 

RICHARDSON.— The Practical Horseshoer: 
Being a Collection of Articles on Horseshoeing in all its Branches' 
which have appeared from time to time in the columns of " 'I he 
Blacksmith and Wheelwright," etc. Compiled and edited by M. T. 
Richardson. 174 illustrations $1.00 

ROPER. — Instructions and Suggestions for Engineers and 
Firemen : 
By Stephen Roper, Engineer. i8mo. Morocco . $2.00 

ROPER.— The Steam Boiler: Its Care and Management: 
By Stephen Roper, Engineer. i2mo., tuck, gilt edges. $2.00 

ROPER.— The Young Engineer's Own Book: 

Containing an Explanation of the Principle and Theories on which 
the Steam Engine as a Prime Mover is Based. By Stephen Roper. 
Engineer. 160 illustrations, 363 pages. i8mo., tuck . $2.50 

ROSE.— Modem Steam- Engines: 

An Elementary Treatise upon the Steam-Engine, written in Plain 
language ; for Use in the Workshop as well as in the Drawing Office. 
Giving Full Explanation; of the Construction of Modern Stearr. 
Engines : Including Diagrams showing their Actual operation. To- 
gether with Complete but Simple Explanations of the operations of 
Various Kinds of Valves, Valve Motions, and Link Motions, etc., 
thereby Enabling the Ordinary Engineer to clearly Understand the 
Principles Involved in their Construction and Use, and to Plot out 
their Movements upon the Drawing Board. By Joshua ROSE. M. E. 
Illustrated by 422 engravings. Revised. 358 pp. . . $6.00 

ROSE.— Steam Boilers: 

A Practical Treatise on Boiler Construction and Exam/nation, for the 
Use of Practical Boiler Makers, Boiler Users, and Inspectors; and 
embracing in plain figures all the calculations necessary in Designing 
or Classifying Steam Boilers. By Joshua Rose, M. E. Illustrated 
by 73 engravings. 250 pages. 8vo $2.50 

iSCHRIBER. — The Complete Carriage and Wagon Painter: 
A Concise Compendium of the Art of Painting Carriages, Wagons, 
and Sleighs, embracing Full Directions in all the Various Branches, 
including Lettering, Scrolling, Ornamenting, Striping, Varnishing, 
and Coloring, with numerous Recipes for Mixing Colors. 73 Illus- 
trations. 177 pp. i2mo - $1.00 



























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